More about 'avere' and other irregular verbs - 'volere, fare'
With some verbs, when the endings -are, -ere or -ire are removed, you are left with a stem to which the endings that indicate 'I', 'you', 'we', etc. can be added.
Other common verbs change much more radically. They are known as irregular verbs and include avere, to have, fare, 'to do', volere, 'to want', and andare, 'to go'.
avere
(io) ho
(tu) hai
(lei) ha
(noi) abbiamo
(voi) avete
(loro)hanno
to have
I have (got)
you have (got)
you have (got)
we have (got)
you have (got)
they have (got)
fare
(io) faccio
(tu) fai
(lei) fa
(noi) facciamo
(voi) fate
(loro) fanno