You can have a number of point-of-view characters in your story. The main character does not have to be the only one.
The main character is the character through whom we experience the story, first hand, so giving them POV is a good choice, often necessary.
Then there's the protagonist. They are the mover of the plot and the one that fights the antagonist.
The main character and the protagonist can be the same, but they don't have to be. (The terms "main character", "protagonist" and "hero" are often used to describe a character that is both a main character and a protagonist.)
Examples of where the main character and the protagonist aren't the same are "Atonement" and "To Kill a Mockingbird".
The antagonist may, or may not have POV. If you write crime or mystery it could be directly problematic, if you write suspense, it could give your story an extra edge (e.g. knowing the villain placed the bomb in the basement gives an extra spark to the living room conversation...)
Here's a rule of thumb I use (and disobey when I feel the need to):
Give the character that has the most to lose in the scene POV.
If you have a scene where some insignificant side character has the most to lose, consider cutting the scene, or, if it has something vital to say, compact it into a narrative transport (i.e. a paragraph or two just telling before you move the story to the next section/scene of active "showing").
Figuring out who's insignificant or not could be as simple as how broad or narrow your story should be or as complex as cutting to the core of stuff like message and theme... It is, after all, the same as figuring out what scenes go into your story, so you may have to write the first draft before you know for sure...