What is the difference between a boomer and a sooner?

The "boomers" were a group (most notably David L. Payne, for whom Payne County, OK is named) who agitated for more than ten years prior to 1889 to open Oklahoma to settlement. The "sooners" were those who illegally crossed the line prior to the opening gun at high noon on April 22, 1889 in order to stake claims to the best land. Most "sooners" planned to immediately resell their claims at a profit.

I'm guessing a 'fragment'. read over the sentence and question again before you move on.