A compound sentence is a sentence made up of two or more independent clauses but no subordinate clauses.
The clauses in a compound sentence are usually joined by conjunctions and/or some kind of punctuation.
Example: Authority is a stubborn bear, yet he is oft led by the nose with gold.
(The two clauses are joined by the conjunction yet. Note that both clauses have a subject and a verb: authority is in the first clause and he is led in the second clause.)