Pixel is the basic unit of digital images. Each pixel represents a tiny portion of the original image, with more pixels providing a more accurate representation. Pixels are arranged in a grid and can be represented by dots or squares. Color depth refers to the number of colors an image can display, ranging from 2 colors for 1-bit images up to over 16 million colors for 24-bit images. Images are composed of either raster pixels or vector paths, with raster being a grid of pixels and vector using mathematical points.