Are sidechains really new? People have been talking a lot about side chains, but I thought this has been around for a while under a different name. Coins like Namecoin, Devcoin, ixcoin, i0coin, groupcoin, etc are all merge mined and have existed long before I ever heard the term "Side Chain". 

Am I correct in my assumption that side chains are just a rose by another name (previously merge mined coins)? Or is there something I am missing here?
A side chain is a blockchain that runs parallel to the main bitcoin blockchain and can synchronize with it directly, allowing decentralized value transfer between the two chains. A user is able to essentially lock up a certain amount of coin on the main bitcoin block chain which then frees up an equivalent amount of coin on the side chain. This side chain may be either a sidechain compatible altcoin or just some test ground for new Bitcoin features. The coin that was transferred to the side chain can be returned back to the main bitcoin blockchain at any time. The value transferred back will be the same as the value transferred out.