Grid is the original compact unit frame addon.
The compact grid of units lets you select a group member quickly, while keeping a good overview of the whole group. Grid is designed to show you only what you need to know, and not overload you with irrelevant information. It is highly configurable, letting you choose exactly what is shown, and how it’s shown. There are also many plugins that add even more features!
For options, type /grid, right-click the tab on the Grid layout frame, or right-click the Grid icon on your minimap or DataBroker display.