Recognize an infinitive when you see one.
To eat, to sleep, to dream, to strive, to achieve,—are all known as infinitives. An infinitive will almost certainly begin with ‘to’ followed by the simple form of the verb, like this: to + verb = infinitive
Note: Because an infinitive is not a verb, you cannot add s, es, ed, or ing to the end.

Infinitives can be used as nouns, adjectives, or adverbs. Look at these examples:
To read is the only hobby of Suresh in his free time.
To read functions as a noun because it is the subject of the sentence.
No matter how fascinating the subject of discussion is, Priya refuses to take interest in it. To take functions as a noun because it is the direct object for the verb refuses.

Wherever John travels, he always carries a book to read with him.
To read functions as an adjective because it modifies book.
Richard braved the icy rain to throw the smelly squid eyeball stew into the apartment dumpster.
To throw functions as an adverb because it explains why Richard braved the inclement weather.