Everything is mentioned in the code .But be careful while executing it. This is doing lots of sorts to get the ranking and it is on different columns. Thus it will do lots of sorts and if your system is alredy under pressure this query might add to your perf issue. I would suggest that you start using one of the counter and comment others and then proceed to make sure that it doesnt put the pressure on the system.
Also, this query will work on SQL server 2008 and compability 100 and above.