How to I find number of test cases executed for a period and number of test cases executed by tester in QC, please explain in me in detail as I am novice to QC
I've answered your question in two parts to give you some flexibility when trying either of these solutions out.
To find the number of test cases executed for a period you can use the Live Analysis option from Test Lab. When you add a graph choose the Progress option and accept the defaults this should get you something very quickly.
For the second part of your question, again use Live Analysis in Test Lab and this time when you add a graph select Summary, change the Group-by drop down to Tester and set the X-axis drop down to Test Set.
It is very likely that your tests are structured differently to mine in Q.C. FYI I have a test suite set as a folder and underneath that I have group of tests grouped as a test set.
There are more complicated answers where you can create customised reports within the Dashboard module - but as you're a novice Q.C. user I haven't recommended any of those.
Hope this helps, Steve.