A group of words that begins with a preposition and ends noun or pronoun?

That's a great description! What you're describing is called a prepositional phrase.

Here's a breakdown:

* Preposition: A word that shows the relationship between a noun or pronoun and another word in the sentence (e.g., "on," "in," "under," "with").

* Noun or Pronoun: The word that the preposition is referring to.

Examples of Prepositional Phrases:

* on the table (preposition: "on," noun: "table")

* in the garden (preposition: "in," noun: "garden")

* under the bed (preposition: "under," noun: "bed")

* with her friends (preposition: "with," pronoun: "her")

Let me know if you'd like more examples or have any other grammar questions!