A PAMM account is where you give trading control of your account to a money manager.
The money manager will execute one trade on a master account that will then split the deal across many other accounts according to the ratio that he has been set.
In theory it is a great system. One deal can be split across lots of different accounts according to each individuals risk appetite. The trouble comes when the money managers actual performance doesn't bear any resemblance to the performance that he sold you on.
Most PAMM managers will not be very good. You have to be very careful. If you are convinced this is the road to your riches and you have found a good money manager then go for it, but be sensible. only give him a tiny fraction of your bank roll, don't listen to them telling you about minimum amounts, you must only deposit what you are able to afford to lose whilst you are test driving him.
pay attention to how much spread he widens the standard spread by to get a nice rebate from the broker. also look at his profit split (shouldn't be more than 25%) and please make sure that there is no minimum redemption period and that you retain ultimate control over your account.
personally, i'd stay clear. i think most of them are terrible.