I firmly believe that all of us have OCD to a certain level or extent.
ompulsive disorder (OCD) is a mental disorder where people feel the need to check things repeatedly, perform certain routines repeatedly
Yes, this is correct. I have OCD and while it does not "rule" my every day life.; it can cause issues at times.
Interestingly,cause of obsessive-compulsive disorder is concerned with identifying the biological risk factors involved in the expression of obsessive-compulsive disorder 
That explanation was a bit over my head. Can you express the same info in "laymans" terms, please?
Obsessive–compulsive disorder
Obsessive–compulsive disorder (OCD) is a mental disorder in which a person feels the need to perform certain routines repeatedly (called "compulsions"), or has certain thoughts repeatedly (called "obsessions"). The person is unable to control either the thoughts or activities for more than a short period of time. Common compulsions include hand washing, counting of things, and checking to see if a door is locked. Some may have difficulty throwing things out. These activities occur to such
Arithmomania
Arithmomania is a mental disorder that may be seen as an expression of obsessive–compulsive disorder (OCD). Individuals suffering from this disorder have a strong need to count their actions or objects in their surroundings.
Sufferers may for instance feel compelled to count the steps while ascending or descending a flight of stairs or to count the number of letters in words. They often feel it is necessary to perform an action a certain number of times to prevent alleged calamities. Other examples include counting tiles on the floor or