Sentences are made of two parts: the subject and the predicate.
The subject is the person or thing that acts or is described in the sentence. The predicate, on the other hand, is that action or description.
Complete sentences need both the subject and the predicate.
Sentences can be broken down into clauses. For example:
The boy is going to the school, and he is going to eat there.
This is a complete sentence composed of two clauses. There are mainly two types of clauses:
independent clauses and subordinate clauses.
Independent clauses act as complete sentences, while subordinate clauses cannot stand alone and need another clause to complete their meaning. For example:
Independent clause: “The boy went to the school.”
Subordinate clause: “After the boy went to the school…”
A group of two or more grammatically linked words that do not have subject and predicate is a phrase. For example:
The girl is at home, and tomorrow she is going to the amusement park.
You can see that “the amusement park” is a phrase located in the second clause of the complete sentence above.
Phrases act like parts of speech inside clauses. That is, they can act as nouns, adjectives, adverbs and so on.
_From English Grammar 101_