Scrotum:
You are dealt 5 cards. Preflop, you decide which cards (n=1-5) that you want to play and set your hand such that everyone can see the number you are keeping. You must play every card you keep, interacting with the standard flop, turn, and river that are on the board. For example, if you keep two pair (4 cards) and the board matches one of them, you play the one from the board for a boat. Another example, if you keep trips and the board has a pair, you also make a boat. Alternatively, you keep trips and the case card hits, then you have quads. Four to a flush means you have a flush when there is one card of your suit that hits. You can also keep all 5, ignoring the board with a pat hand.
Scrotum8:
Scrotum, but adding a split with the lowest 8-or-less qualifying low. Keeping four small cards of a suit is extremely powerful, as there is the opportunity to scoop with a nice flush. Steel wheel = $$$ (nut low with a dominating high).
Very tricky and fun game, with a lot of reading of people involved. Lots of choices for what to keep to maximize payouts and disguise hands!