The infinitive phrase, also known as the infinitive clause, is a group of words that combines an infinitive verb and complements or objects, plus modifiers to the infinitive and to the complements or objects.
The infinitive verb, when used as a noun, adjective or adverb, is preceded by the word ‘to.’  With infinitive phrase usage, when the infinitive follows some verbs as the direct object, the ‘to’ may be dropped. (She helped (to) bake the cake)

the infinitive phrase – examples of usage

She offered to pay for the goods.
Noun. Infinitive: To pay for …(direct noun object) the goods

To see clearly, she moved closer to the stage.
Adverb. Infinitive: To see clearly, … (modifying verb) moved.

Let’s ask which way to go.
Adjective Infinitive: To go … (adjective modifying noun) way

When an infinitive phrase breaks the sentence, a comma is used to separate out the phrase.
The infinitive phrase contains an infinitive as its main or only verb form.
The infinitive phrase, or infinitive clause, is a group of words that combines an infinitive verb and complements or objects, plus modifiers to the infinitive and to the complements/objects. The infinitive phrase, when used as a noun, adjective or adverb is preceded by the word ‘to.’