Spanish verbs are one of the most complex areas of Spanish grammar. The Spanish verb system is separated into 11 distinct tenses, referring to both time and mood. Seven "compound tenses" also exist, and have the auxiliary verb haber along with the past participle. Verbs can be used in other forms such as the present progressive tense but this is not considered an official conjugation of the verb (ex. Voy a ir - I'm going to go).
A large number of everyday use verbs are irregular. The rest fall into one of three regular conjugations, which have infinitives ending in -ar, -er, or -ir. The -ar verbs are the most common, and new verbs usually adapt the -ar form. The -er and -ir verbs are far fewer and tend to be more irregular.
There are also many semi-regular verbs which show vowel alternation conditioned by stress. These include the e->i, e->ie, and o->ue verbs.
Read more about Spanish Verb Forms. [Source]