Conjugated Verb or Infinitive?

The Spanish infinitive (a verb ending in -ar, -er, or -ir) is often used after a conjugated verb (a verb that is changed to reflect the subject).

Example:
Quiero bailar. (I want to dance.)
Quiero is a conjugated verb. It goes with the subject is "yo."
Bailar is an infinitive verb. It ends with -ar.

There are exceptions, but this "rule" applies in most cases and in all cases in Spanish I-II.