Every photo already contains a palette — the sunset you liked, the room you want to repaint around, the poster whose colors just work. This pulls out the six that dominate, names them, and hands you the codes.
Tapping single pixels of a photo gives you camera noise — one pixel of that "blue" sky might be #7FA8CF and its neighbor #85AECB. Clustering thousands of pixels averages the noise out and finds the colors your eye actually reads. For a single precise pixel (a logo, a UI element), the detector's photo mode is the right tool; for "what palette is this scene," this one is. Check any pair of extracted colors for text use with the contrast checker.