I trying to learn how futures market work. I know what continuous contract are and how they are generated, but when i see quotes they are listed as GC1 and GC2. what is the difference between GC1 and GC2(gold) or HG1 to HG2(in case of copper). Is it related to maturity ?

GCn are the 'generic' names for the gold contracts. GC1 is the first (most nearby) contract, GC2 the second, and so on.You can also refer to contracts using the specific (not generic) names. For example GCM5 is the June 2015 contract (M=June, 5=2015).At this time (April 11, 2015) GC1 is in fact equal to GCM5, i.e. the june contract is the first contract (and GC2 is equal to GCQ5, i.e. August). However this changes over time as contracts expire and new contracts take their place, and the CDEF command controls the details of how the Generic Contracts work (in particular, when you retrieve historical data for GC1 what kind of price adjustment if any will be performed. This is controlled by CDEF Generic Rolls). For historical research Generic Contracts allow you to use continuous (also called adjusted) prices that take into account the contract roll effect.Other useful commands are DES (to retrieve the description for GC1 type GC1 Comdty DES) and CT (contract table) which allows you to see all available contracts.In Gold there are usually 6 or 7 contracts in each calendar year, and several years (2015 to 2020) are listed though in practice many of these contracts are quite inactive.

Thanks, for clarifying the doubt. Now i get it what's the difference between gc1 and gc2.