Purists say there are 8: First Person Protagonist, Third Person Protagonist, First Person Supporting Character, Third Person Supporting Character, First Person Minor Character, Third Person Minor Character, First Person Shifting, and Third Person Shifting.
Of course, there can be variations on the basics. Harper Lee wrote To Kill a Mockingbird in First Person using Restricted Omniscient. James Jones wrote From Here to Eternity in Third Person Unrestricted Omniscient. John LeCarre wrote The Spy Who Came in From the Cold in Third Person Restricted Omniscient.
The important thing is to choose your viewpoint character and stay in that viewpoint unless there is a compelling reason to change. Beware of the literary sin known as "head hopping" in which each person who speaks also thinks, meaning viewpoint shifts back and forth--sometimes as frequently as a dog wags its tail. (That makes me think of a historical romance author back in the 1980's who even had a mouse, I think it was, with a viewpoint!)
Many romance novels are written with shifting viewpoint used in intense emotional scenes, such as lovemaking. When the viewpoint change is obvious, and it works in that particular scene, don't be afraid to break the rules.
In other words, learn the rules first, then learn how to break them so that you make seamless viewpoint shifts that carries readers along rather than jars them out of the story and sends them backtracking to see who is speaking or thinking.