Religious titles in Islam and Christianity
Question

What is the difference between the titles "Sheik" and "Imam" ? What qualifications must one have in order to attain these titles?.
Praise be to Allah.The religion which Allaah has chosen is the religion of Tawheed, Islam, for which He sent the Messengers and revealed the Books. It is by His grace towards His slaves that He has preserved this religion and decreed that it will survive and continue and its basic principles will be preserved through the sincere and devout scholars who are entrusted with the Revelation and who bear that trust and deliver it as enjoined by their Lord.  
Among previous nations in history there has been distortion and changing of the contents of the messages of the Prophets to a great extent, because most of their scholars betrayed the trust and sold the covenant of Allaah for a small price. They were misled by their whims and desires and by the shaytaan, and they introduced into the religion things for which Allaah gave no permission. One of the most serious ways in which they distorted the message of the Prophets was by introducing the principle of al-waasitah (mediation) between Allaah and His creation, between the almighty Lord and His slaves, thus aiming to protect the thrones of the tyrants who oppressed the people thereby and held their destiny in their hands, through the body that spoke in the name of “heaven”. They invented names and titles for this organization and classified them in varying degrees and levels, where the clergyman could progress through the ranks that had been invented in the name of “the Lord” until he reached the position of acting as the deputy of “God” as the “high priest” or “pope”. 
The English historian Wills said in his book, Milestones of Human History (3/270):  
But even though the fully-developed Christianity of the fourth century preserved the teachings of Jesus in the Gospels as its foundation, it was in essence a sacerdotal religion of the type that had been familiar to people for thousands of years. The altar was the focus of its elaborate rituals and the essential act of worship was the sacrifice consecrated by the priest for the Mass, and it had a structure that quickly formed, composed of the deacons, priests and bishops. End quote. 
This body developed its authority and its method of organization from the political hierarchy of the Roman Empire as Shaykh Safar al-Hawaali said in his book al-‘Ulmaaniyyah (79): 
The presence of priests and monks within the Roman Empire helped to support their position and reinforce it, because they copied from the political system and hierarchy of the state the idea of creating a priestly system and hierarchy. Just as the state system resembled a pyramid with the emperor at the top and the troops at the bottom, the church system also resembled a pyramid, with the pope at the top and the priests at the bottom. As a result of the principle of separating church and state, the empire took care of sponsoring the church hierarchy, and did not find anything in it that contradicted or opposed the state hierarchy. Thus it was settled and became strong. End quote. 
But in the sharee’ah of Islam that was divinely protected, you do not find the kind of class system that could reinforce tyranny and oppression, and you can only find texts which speak of equality among all people and state that the best of them are those who are most pious and closest to Allaah and who follow His laws most closely. 
Allaah says (interpretation of the meaning): 
“Verily, the most honourable of you with Allaah is that (believer) who has At‑Taqwa [i.e. he is one of the Muttaqoon (the pious)]”
[al-Hujuraat 49:13] 
“And for all, there will be degrees according to that which they did, that He (Allaah) may recompense them in full for their deeds. And they will not be wronged”
[al-Ahqaaf 46:19]
Hence the essence of Islamic sharee’ah is based on cancelling out the mediation of bandits who come between the people and Allaah in the name of “mediation” or “intercession”. Islam attributes this attitude to the mushrikeen who fought the message of Tawheed, of whom Allaah says (interpretation of the meaning): 
“And they worship besides Allaah things that harm them not, nor profit them, and they say: ‘These are our intercessors with Allaah.’ Say: ‘Do you inform Allaah of that which He knows not in the heavens and on the earth?’ Glorified and Exalted is He above all that which they associate as partners (with Him)!”
[Yoonus 10:18]
The guided French scholar Naasir al-Deen Dinet said: 
The issue of mediation was one of the major issues in which Islam superseded all other religions, because there is no intermediary between Allaah and His slave. There are no priests or monks in Islam; these intermediaries are the cause of all evil in other religions and that is indeed the case no matter what their beliefs and no matter how sincere they are and how good their intentions. The Messiah himself understood that. Did he not drive the sellers out of the temple? But his followers do not act as he did, and today if Jesus were to return how many like the sellers in the temple would he drive out?  End quote from al-‘Ulmaaniyyah (p. 81). 
As for the status of the fuqaha’ and scholars in Islam, it is purely academic, i.e., whether a person has enough knowledge to qualify him to talk about religion is based on his studies and academic qualifications and what he has learned from universities, study circles and books. It has nothing to do with any religious hierarchical body or priestly rituals that give them authority in the name of the Lord. Rather it is a level of specialized knowledge – as in any other field of knowledge studied by specialists. They may be correct or incorrect, and they are subject to criticism on the basis of evidence. None of them has any authority or power to declare things halaal or haraam, or to issue commands and prohibitions, except the Lord of the Worlds. They are no more than conveyors of His laws, and teachers who tell the people of what was revealed from the Lord of the Worlds. Moreover, as we have pointed out, they are not infallible in their understanding of the message brought by the Messenger of Allaah (peace and blessings of Allaah be upon him), or in the way they preserve it and convey it. Rather the infallible ruling, which Falsehood cannot come to it from before it or behind it (cf. Fussilat 41:42), and which is to be referred to in the case of a dispute, is the Revelation of Allaah, may He be exalted: His Holy Book and what is narrated in saheeh reports from the Prophet (peace and blessings of Allaah be upon him), then that on which there is consensus among the ummah, for his ummah cannot agree on misguidance. 
The titles and names that the scholars bestow on some of them, or that the people bestow on them, are only referring to the level of knowledge that a person acquires of the rulings of sharee’ah. There may also be a kind of distinguishing the type of knowledge in which a person has specialized, such as faqeeh and mufti for those who have specialized in fiqh and issuing fatwas, respectively, or mufassir for the one who has specialized in tafseer or commentary on the Book of Allaah, or muhaddith and hafiz for those who have specialized in the study of hadeeth. 
The scholar may also be given titles of praise for his vast knowledge and learning, such as Shaykh al-Islam or ‘Allaamah or Imam and other such titles which ascribe knowledge and learning to those who are entitled to them. In no way are they meant as indicators of priestly status that has been earned in a gradual manner through stages of devotion and monasticism.  
Even describing the academic level by using these titles is not something precise, such that the one who reaches a certain level will be called by a different name than someone who has reached a lower level. Rather they are relative descriptions and do not refer to precise distinctions between one level and another, and they are not indicative of different levels of knowledge, rather they point to general praise or particular specializations. 
There is no precise difference between the titles of imam, ‘aalim and Shaykh and it is not permissible for anyone to understand their usage in books or by scholars in terms of the innovations of other nations with regard to clergymen and priests. 
And Allaah knows best.