A hair catcher is another name for a drain cover or drain protector. They are the same thing, though some companies call them by different names. The purpose of a drain cover is to prevent anything besides water and soap from going down your drain. The primary thing a drain cover will stop is hair. This is important because hair will flow down drains easily, it is gross to clean up, and hair will create serious clogs in your pipes over time. Before causing a clog hair will slow down the flow of water, causing your shower to fill at the bottom as you run the water.