A simple sentence is a sentence that consists of one independent clause.
An independent clause is a clause that can stand alone as a sentence. Every sentence must contain a subject and predicate and express a complete thought. Independent clauses fulfill these criteria.
This is the case in the given sentence. It makes sense and has one subject and one predicate.
A compound sentence is a sentence that consists of at least two independent clauses connected by a comma and conjunction or by a semicolon.
A complex sentence is a sentence that consists of one independent clause and at least one subordinate clause. Unlike independent clauses, subordinate clauses don't contain all of the elements I've listed above, which is why they can't stay alone as sentences.
Liberty - the state of being free. Freedom is a key to living life. That’s why it is called the Statue of Liberty and everything in it symbolizes freedom.
