Aser...
Rin: In basic form it's multiplying the amount of landings you make by a factor...The minimum factor being 2 ...This accounts for the high power setting for departure and arrival of a specific flight...These numbers are entered (should be) into the a/c maintenance record by the engineers and become part of timed life/RIN components histories...
Most components have a timed life as you know, this life being predicated on normal usage...If the mission requirement is, for example: logging or firefighting that gives you a demand for 15 to 60 high power events per hour, each demanding around the same requirements as a landing, but with no touchdown...The machine has worked a lot harder than say, charter ops...
So the maintenance dept will (should) factor each flight hour to simulate the additional WORK the a/c has done with all the additional power cycles...
The factor used , is variable around the world from my experience, and can be a point of serious contention between pilots and management
if you work the machines hard. Just because a component has a timed life of X hours in normal use (what's normal?) But if your mission requirement calls for 70 high/low power events per hour...The component shouldn't be expected to last the same time as if it had a comfortable 2 events per hour...
As a good example, the B747 shuttles that were tried in the LA basin years ago, failed in part from the 3 cycles (x2) per hour of RIN put on airframes designed for landings every 5.5 hours or so (that was the rumor at the time)
Hope this makes sense?