Panel has several related meanings, all connected to the idea of a flat section or a group serving a specific purpose:

1. A flat, usually rectangular piece that forms part of something larger. The wooden squares in a fancy door are panels. Solar panels on a roof are flat sections that capture sunlight. A comic strip is divided into panels, each showing a different moment in the story. Cars have body panels (the metal sections that form the outer surface), and houses once commonly had walls made of separate wooden panels. When something is paneled, it's covered or decorated with these sections: a wood-paneled library has walls made of fitted wooden boards.
2. A group of people assembled to discuss something, answer questions, or make decisions. At a science fair, a panel of judges evaluates the projects. On a quiz show, a panel of experts might answer questions. When authors visit a school, they might sit on a panel to discuss their books, with each author taking turns speaking. A court might have a jury panel. These people are called panelists. The word suggests that each person brings different knowledge or perspective, and together they're supposed to reach better answers or decisions than any one person could alone.