For my non-writing readers, plotters start off their writing with not just a story idea, but a plot, characters, character arcs, structured flow, high and low points, scene outlines, maps, etc. etc. Pantsers often have just a story idea, and then just write whatever comes out, navigating by the seat of their pants.
Plotters have the advantage of knowing where their story is going, but too much structure may constrain their creativity. Or result in major rework to adjust all that structure to a new direction. Pantsers can just be creative and write, but at some point they will have to rearrange and edit to fit everything into some sort of structure. And maybe throw a lot of their wok away. Because, while readers love great dialogue and action scenes and description, they also want to see things like plot and character issues. As do agents and publisher and editors.