The infinitive (el infinitivo) is the basic form of a verb that you find when you look it up in a dictionary.
Three types of verbs based on their infinitive form
In Spanish there are only three possible endings for the infinitives:
Infinitive ending in -ar
hablar, caminar, cantar...
Infinitive ending in -er
comer, beber, aprender...
Infinitive ending in -ir
vivir, dormir, sentir...