A complete sentence contains at least a subject and a verb, with all of the words being used in the sentence arranged in such a way that they express a complete thought.
There are four ways to Structure a Sentence.
Simple Sentence, or Independent Clause. This sentence has one subject and one verb, although it may employ adjectives and adverbs. The independent Clause cannot be joined by another Independent or Subordinate Clause.
I like reading books.
My brother likes to quote movies.
Compound Sentence. This sentence is made by two or more Independent Clauses joined by either a Coordinating Conjunction or a semicolon. Like Simple Sentences, the Compound Sentence cannot contain a Subordinate Clause.
I like reading books; my brother likes to quote movies.
We looked everywhere but couldn't find him.
Complex Sentence. The Complex Sentences contain one Independent Clause and at least one Dependent Clause connected by a Subordinating Conjunction. The Independent Clause is called the "Main Clause."
I like to read my book out loud when my brother is quoting the movie.
I typed my essay on a computer since I am out of paper.
Compound-Complex Sentence. This sentence contains at least two Independent Clauses and at least one Subordinate Clause. The Subordinate Clause may be a part of one of the Independent Clauses.
When I type too fast, my spelling is poor, and I spend too much time editing.
I planned to go to school, but I cannot leave the house until my brother proof reads my essay.