The infinitive is a verb in its most basic form as it shows no information about tense, person or aspect of the verb.
The infinitive may or may not have "to" before it. If preceded by "to", the infinitive is called the full infinitive (or to-infinitive).
- I want to see this movie.
- It is time to go.
Otherwise, the infinitive is called the bare infinitive (use the hyperlink to learn more).
- She might be amazed.
- I should go now.