As per title. Also what do developers hope to achieve from the process and have you ever done any of this type of testing, if so what games did you test and do you think the process could be improved?

It's pretty self-explanatory. They test the beta model of the game and report back or the game observes in the background how the game handles intended player actions, what kinds of bugs arise and what types of problems are there. If it's an Online game, it's also there to test server strain sometimes too.