The "Panda Helpers" are a feature in which the computer AI will play a turn on behalf of a player who is taking too long to play. Previously, a player who took too long to play would simply auto-forfeit the match. But neither winning by auto-forfeit nor losing by auto-forfeit is much fun, so Panda Helpers were introduced to keep matches out of the auto-forfeit state.
Currently the Panda Helpers will play for a registered player after 3 days and for an anonymous player after 2 days. But if neither player is actively playing the game then the Panda Helpers will simply resign rather than having the computer AI play against itself.
Note that the Panda Helpers' AI is currently not very smart (this is by design). It generally plays a 3- or 4-letter word and sometimes gets lucky with regard to points or strategy, but it's not trying hard to score well. Thus, it is generally to your advantage to play your turn yourself rather than let the Panda Helpers play for you.