There are three types of sentences in the English language: simple sentences, compound sentences and complex sentences.
The simple sentences are those which contain a subject and a verb, and they express a complete thought. For example: My colleague likes running.
The compound sentences contain two simple sentences, joined by a coordinating conjunction (for, and, nor, but, or , yet, so). Example: I tried to reach for the top shelf, but I couldn’t.
The complex sentence is formed by simple or compound sentences, but are joined by subordinating conjunctions like: because, since, after, although, etc. Example: I couldn’t do my homework because I had to stay up and guard the house.
Another type of complex sentences are those with adjective clauses. Example: The man who looked at my car gave me a phone call just as I came in.