In the television industry, a lower third is a graphic overlay placed in the title-safe lower area of the screen, though not necessarily the entire lower third of it, as the name suggests.
In its simplest form, a lower third can just be text overlaying the video. Frequently this text is white with a drop shadow to make the words easier to read. A lower third can also contain graphical elements such as boxes, images or shading. Some lower thirds have animated backgrounds and text.