The woman in the blue coat is looking for her dog. The above sentence contains two prepositional phrases:
"in the blue coat" and "for her dog."
A prepositional phrase begins with a preposition, such as "in" or "for" and ends with a noun. There are hundreds of different prepositions, so they are very commonly used and very important to understand. Why are prepositional phrases important? They provide important information on location, descriptions of people and things, relationships, time, and ideas.
The best way to learn how to use prepositional phrases is to read English. Over time you will learn how they are used and which ones to use. Below are some examples.
She spilled coffee on her report for class.
prepositional phrases: on her report and for class
In this example the prepositional phrases provide important information about where something happened and the reason for her concern.