This application shows the current CPU usage in a floating rectangular meter, or in your Dock icon, or both. This information is useful for determining how hard your computer is being worked. Your computer may behave slowly or run hot when the processor is being worked hard.
The text is completely transparent, and the opacity of the meter's background is directly tied to the CPU usage (for example, the backdrop of the meter in the screenshot is 63% opaque). Also, if you have more than one processor, the meter will have multiple cells, and in each one, the CPU number will be shown below the percentage.