Joe had an excellent note about it yesterday, #msg-883651
It's not something you can buy or sell. It's and indicator. And yet you chart it and watch it sort of like a stock since it tends to act like one. Camp decides what the buy/sell levels are to be set at for the day and publishes them on his website. How he comes up with them isn't known. Something to do with 20 years of capturing the data feeds of the markets and statistics. The important thing to know is that when the PREM (which is the difference between the SPX cash and SPX futures) hits the buy/sell levels or more, what then is suppose to happen. The computers are programed to either buy or sell when the levels get hit. The big money is making a move. Read the message Joe posted and it will give you ideas on what and how it is used. If you still have questions ask away.