SESMA is a monitoring system which detects certain operating parameters (varying on each type of aircraft) and records them on a Quick Access Recorder. The QAR tapes are then sent for analysis and if any parameter has been exceeded, the reason for it is investigated. It is a particularly useful gadget for detecting trends such as deep landings. It can be used to see if one particular pilot is doing this, in which case he can be sent for specific refresher training, or if it is a fleet wide trend, in which case, wider publicity can be employed, perhaps using changes to a simulator check.
As to the parameters themselves, they differ from type to type. They aren't generally published within the airline as they generally give a little leeway over company SOPs, which are (quite correctly) reasonably conservative.
Someone else can possibly come up with a little more detail.
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Just want to say good luck, we're all counting on you .......