Assuming you mean in live chess, it's likely a means to hide the bots that are available to play against from your open seeks list.
A number of users, and I have no idea why, were upset when they saw that there were engines set up to ensure that there would always be a game available in the new version of live chess so this is probably in response to those complaints.
When the Seek Filter comes uup there's and option to "Hide Computers"... what does that mean??? thanks