Infinitives refer to a verb as a noun (or adjective/adverb): I like to eat. What do you like? (what is the direct object?) To eat. It is being used as a noun. Prepositional phrases use "to" as any...
Below is an example a sentence with a noun phrase and three prepositional phrases: A group of students (noun phrases) were sitting on a bench (prepositional phrase) in the garden (prepositional...