The verb ending changes depending on the subject of the verb. 

Je fais, tu fais, il fait, Marie fait etc, as per the lesson. Was your question related to a more specific example ? 

As you will find in further lessons, verb conjugation according to the subject/tense/mood is a major topic in French grammar ! 

When the subject is I the verb has to end in aid and when the subject is him  or on it is is in air . 

When the subject is I the verb has to end in aid and when the subject is him  or on it is is in air . 

the s ending is reserved for je and tu pronouns. While t ending it for il,elle and on pronouns.

the s ending is reserved for je and tu pronouns. While t ending it for il,elle and on pronouns.