PAMM stands for Percentage Allocation Management Module. PAMM accounts are used as a type of money pooling system that can be used for trading. Investors would fund a Money Managers open fund so that the Money Manager can proceed to trade with it.
An Investor will gain profits/losses from any trading made by their Money Manager. In turn, the Money Manager would make a profit from fees made from trading these invested funds. The fees are decided by the Money Manager when creating their fund and an Investor can decide whether or not to proceed with investing.
For more information on how the PAMM system functions, click here.