This form is used to describe states, information and concepts of a very general nature.
You can also use simple present to describe routines or habits.
Sequence of actions
When you describe how one action follows another one - like in technical manuals - you use simple present.
Verb (infinitive) for all subjects except 3(rd) person singular.
For 3(rd)person singular subjects he, she, it or anything that can be replaced by these you add an -s to the verb.
Verbs ending in sibilants a 's'- or 'sh'-sound get an -es.
have - has, do - does, go - goes
The 3(rd) person forms of 'be' ('is') and other auxiliaries also called 'helping verbs', like 'can' or 'must' are not changed, of course.