That's conjugation, like putting the s after the verb in third person in english but more complicated. It's like this:
Infinitive: a avea
https://dexonline.ro also has a conjugator which will come in handy. To use it search for the verb and click on "conjugări" at the top.
Oliver, I see you study Spanish, Portuguese, Italian and French, because in all our Romance languages the conjugation of the verb agrees with the pronoun, from there that in some occasions the pronoun can be omitted without affecting the meaning of the sentence (except in French ).