There are three...
Italian has three conjugations (le coniugazioni):
first: -are verbs
second: -ere verbs
third: -ire verbs1
Verbs that end in -arre, -irre, and -urre belong to the second conjugation of verbs.
The stress on the infinitive:
Falls on the suffix of the verb: amàre, cadère, preferìre
But, for some -ere verbs, the stress falls within the stem: crèdere, prèndere, difèn…