An infinitive phrase consists of an infinitive and any modifiers or complements the infinitive has. The entire phrase may be used as a noun, an adjective, or an adverb.
Noun: To climb Mount Everest is one of Ann’s goals. [subject of verb is]
Adjective: Any time is a great time to be in New Orleans. [modifying the noun time]
Adverb: We displayed posters to remind everyone of the Earth Day festivities. [modifying the verb displayed]