HEM =
http://www.holdemmanager.net/ A software program used by players to analyze things
Flatting = Calling a raise/bet
Kxs = The K stands for a king, the x refers to any other card in the deck, and the s stands for suited. So this could stand for KQ suited, or K9 suited or K5 suited etc etc. In the same way Qx, would mean a queen with any other card such as QJ or Q8.
SC = Suited Connectors, hands like 67 suited, 89suited, 34suited
Equity against = hard to describe this with my crappy use of english, but it means like your percentage to win the hand against your opponents hand. So AK has approximately 50% equity against QQ whereas JJ has approximately 20% equity against QQ