Prepositions are words that indicate the relationships between various elements within a sentence. In formal English, prepositions are almost always followed by objects.
e.g. The policeman shot (verb) the man (object) with (preposition identifying the man being shot) a knife.
e.g. I put (verb) the pen (direct object) on (preposition indicating the position of the pen) the table (indirect object).
e.g. I put (verb) the pen (direct object) under (preposition indicating the position of the pen) the table (indirect object).
Prepositional phrases always consist of the object and the preposition. Prepositional phrases can act as adjectives or adverbs. When they are used as adjectives, they modify nouns and pronouns in the same way single-word adjectives do. When prepositional phrases are used as adverbs, they also act in the same way single-word adverbs and adverb clauses do, modifying adjectives, verbs, and other adverbs.
Prepositional words and phrases are difficult, especially for ESL learners, because different prepositions may impart different meanings to the prepositional words and phrases. Even the same preposition may have different meanings to the same verb.
Break in: enter without permission; interrupt; train; get used to something new.
e.g. A burglar attempted to break in last night but without success.
e.g. Don't break in while someone is talking; it's rude
e.g. The manager has to break the new employees in so that they may know what to do.
e.g. You should break your new car in before you drive on the highway.
This book has hundreds of prepositional words and phrases with explanations and examples, just like the ones illustrated above, for you reference. Improve your English with your mastery of prepositional words and phrases.