lol well an MM is a person who basically does the trade.
Example.
If you sell the account
this is how it would go.
The person Buying the account gives there amount to the MM on rs2.
You tell the MM the password to the account.!
The MM goes on and sees if everything is true.
The MM gives the buyer the password.
The buyer Changes pass/sets recovs,etc.
You get your money from the MM dat was holding it from the buyer.
Its basically A Good Way to trade. As long as you have a TRUSTED MM.
Id go with Highly trusted becuz officials are expensive lol