Impurity (Najasah): its types and how to purify things
Question

What are the types of impurity (Najasah)? Give me examples for each of them, and what is required to cleanse each of them.
Praise be to Allah.This question has requires a lengthy and detailed answer. The jurists have written entire, lengthy chapters which take up dozens of pages. But we will tell you about the types of impurity and how to clean each type in brief, and we will recommend to you some trustworthy sources in which you can find the details of what you have asked about, with evidence.
Firstly:
Types of impurity (Najasah):
Impurity is of two types: that which is impure in and of itself and that which is deemed to be impure.
1.. That which is impure in and of itself: meaning that the essence of the thing is impure, such as faeces, urine, blood, the saliva of a dog; and wine (alcohol) according to most of the scholars. What is meant is that the thing itself is impure.
This type cannot be purified by washing with water, but if it is transformed into another substance, it becomes pure through that transformation, such as wine that turns into vinegar.
2.. That which is deemed to be impure, which is when the impurity comes into contact with something that is pure, such as when urine or blood gets onto clothing that is pure. This type of impurity is called temporary, or is deemed to be impure. This is what can be purified by washing it.
Secondly:
The most common temporary impurities that get onto pure things which then need to be purified are:

Human urine and stools
The urine and stools of animals that cannot be eaten
Madhi (prostatic fluid)
Wadi (thick, white liquid that comes out after urinating)
Blood poured forth, which is the blood that flows when an animal is slaughtered
The blood of menses, postpartum bleeding (Nifas) and irregular bleeding (Istihadah)
The saliva of a dog
Wine (alcohol), according to most of the scholars.

Thirdly:
In terms of severity, impurity (Najasah) may be divided into three categories:

Lesser impurity, such as the urine of an infant boy who is not yet eating solid food, if it gets onto clothes and the like.

The way to purify it is to sprinkle water on it until it covers the entire area. This applies only to the urine of a baby boy. As for the urine of a baby girl, it must be washed and it is not sufficient to sprinkle it.

Intermediate impurity, such as human urine and stools, and the blood of menses and postpartum bleeding. Most impurities are of this type.

The way to purify them is to wash the affected item with water until the impurity disappears. If it has any solid substance, that must be removed before washing it, and it does not matter if the colour remains after washing it.
iii. Greater impurity, which is the saliva of a dog.
The way to purify it is to wash what the dog licked seven times, the first of which must be with earth.
Fourthly:
How to purify impurities.
The things that impurities get onto are of four types:

The ground. If the impurity falls onto dirt or paved ground, then if it has a substance, as in the case of faeces, it must be removed first, then water should be poured on that place until the traces disappear, or it may be buried in clean earth if there is no water.

If it is urine, then water should be poured on the place until all traces of the impurity disappear.

Water. If the impurity falls into water, then the way to purify it is by eliminating the impurity from the water until no trace of it remains in its colour, taste or smell.

That may be done either by removing the water, or if the water changes by itself, or a lot of water is added to it, or it is cleaned by modern methods, until all traces of the impurity disappear.

Clothing and furnishings. If the impurity gets onto clothing or furnishings, they must be washed with water or pure detergents, and they should be rubbed, wrung out and dried until all traces of the impurity disappear. Shoes and Khuffs that are contaminated with impurity may be purified by rubbing them on the ground until all traces of the impurity disappear.
Vessels. If impurity gets into a vessel, it should be washed with water or pure detergents until all traces of the impurity disappear.

For more details and evidence regarding what has been mentioned above, please see: Ash-Sharh Al-Mumti` by Shaykh Al-`Uthaymin (1/414); Mawsu`at Al-Fiqh Al-Islami by At-Tuwaijri (2/327); Al-Fiqh Al-Islami wa Adillatuhu by Az-Zuhayli (1/301); and Risalah fil-Fiqh Al-Muyassar by Shaykh Salih As-Sadlan (p. 26-28).
You may also refer to some reliable websites and books in English in which you can find more details about the issues of impurity and how to purify things on this link and this link.
And Allah knows best.