I didn't understand the questions at first but I think you are just wanting to know the basics of symbols, expiration months etc.
I only look at 2 futures contracts: ES and NQ - both of which trade on the CME. The info for these contracts is set by the exchange so that is the place to start (and it is on the web site I'll see if I can find a link.)
There are 4 dates each year (March, June, Sept, Dec) where the active or front month contract expires. Right now we are trading the June contracts. These contracts expire on the 3rd Friday in the expiration month. So the June contract will expire on June 21. The March (old contract) just expired on the 3rd Fri of March - the 15th.
Rollover:
Rollover is the date when you switch from the old expiring contract to the next month's contract. You do this because the professionals do this and so the liquidity switches to the new contract. The rollover from the March to the June occurred on Thursday March 7th. The rule is that the 3rd Fri is expiration, and the day before the 2nd Friday is the rollover day (it is always a Thursday).
The contract expiration dates carry with them number and letter symbols that are used in the ticker symbol. ES is the base symbol for the EMINI S&P 500. The ticker we are trading now is ES2M. The 2 is the last digit in the year 2002. Last year at this time we would be trading ES1M for 2001. The contract expiration months have a 1 letter symbol:
March = H
June = M
Sept = U
December = Z
So the 4 contracts for ES that will be active this year are ES2H, ES2M, ES2U, ES2Z.
Does this help? I'll post a link to the CME site if I find it.