Variance Analysis of Expenses-PLS Help!!!!

Dear all,

I am in a trouble........I am instructed by my BOSS to  go on client and do Variance Analysis of all the Operating Expenses of the client ............But I Dont Know wat VARIANCE ANALYSIS is ??? he wants me to QUANTIFY  it also............

Now he is not picking up his phone............and i dont know wat i m supposed to do in variance analysis...............Kindly help me guys..........pls lemme know wat this is all about???