Protagonist - The central character of a story.
The Protagonist is the leading or central character, the story revolves around him or her, and it usually attracts the readers emotionally.
Dynamic - A character who changes over time.
Dynamic characters had experiences that lead him/her to undergo changes or substantial transformation through the story, in personality, attitude, a point of view, maturity, etc. And these changes don't tend to be described outright. Rather, his traits are referred to as they change over time.
Static - A character whose traits remain the same.
Unlike, the character described above, static characters don't change much (or nothing at all) through the story, although they can have an interesting personality that attracts people's interest, and can also be protagonists.
Flat - A character with a single dominant trait.
Static characters are similar to the flats one in one way: they don't change or change too little, in the story. But they have significant differences: these characters are simple, only exhibit one or two qualities, don't tend to show any emotional depth, and their role is to support the protagonist. They only play a side role in the story.