This is an example of a simple sentence.
compound sentence.
complex sentence.
compound-complex sentence.

A simple sentence consists of only one clause. A compound sentence consists of two or more independent clauses. A complex sentence has at least one independent clause plus at least one dependent clause. ... Sentence 4 is compound-complex (also known as complex-compound).

martians or other types of aliens represent a unique fear as opposed to zombies. vampires and other types of monsters.   in most sci-fi stories, aliens come from other worlds and have different or more advanced technology.   abductions and experimentation on human bodies that involve these technologies, or the use of these technologies against human beings and the use of unknown "powers", are a type of fear that's different from that of other types of monsters.