A sentence refers to the pair of words which is complete in itself. In other words, a sentence contains a subject and a predicate or it may contain a main clause and one or more subordinate clauses to convey a command, exclamation, question or statement.
Simple subject refers to the basic unit in a sentence. A subject may be referred to a place, person, idea or a thing which describes what the sentence is about. In other words, it does the action and connects with the verb.
Whereas, simple predicate refers to the main verb in the predicate. It informs about the action of the subject.
Hence in the sentence "Everyone in our band is marching."
The simple subject is "Everyone" and the predicate is "In our band is marching." Wherein, simple predicate is "Is marching."
