P5 panels are like mini televisions in that they have many RGB LED lights in a grid. They come in many shapes, styles, and layouts. The panels on this page have a resolution of 64x32. The number 5 in P5 stands for 5mm of spacing between the center of each light. Thus, these panels are 320mm wide by 160mm tall. By utilizing more than one panel, you can daisy chain them together to make much larger panels that behave as one. Each set of panels comes with two 6 inch ribbon cables to daisy chain one to the next, and a single power cord that will handle two panels, and a set of rubber gaskets to make the backside of the panel water resistant.
Below is a great video that explains what a panel is and some of the different ways in which you can run Panels. The second half of the video focuses directly on Colorlight Cards and their configuration. NOTE: The configuration steps in this video are outdated. Both FPP and LEDVision have been through multiple versions since this video. A direct link to the video can be found here: http://videos.xlights.org/xessentials-e26-p5-p10-panels-and-the-colorlight-board_f8084fcc8.html