Merged coins: What's that?

[Quimbo]

I often read about the term "merged coins".
Can somebody explain what that is?
And how does it work?
Does it involve making 1 digital currency out of multiple ones?
Could all coins be merged into Bitcoin at some point?

Thanks in advance!

[MAbtc]

Merged mining allows a miner to mine for more than one blockchain at a time, adding to the hash rates of both coins. As a result, merged mined coins can be mined at very little cost to miners, making it more likely that the merge mined chain remains secure.
http://bitcoin.stackexchange.com/questions/273/how-does-merged-mining-work

[Quimbo]

Merged mining allows a miner to mine for more than one blockchain at a time, adding to the hash rates of both coins. As a result, merged mined coins can be mined at very little cost to miners, making it more likely that the merge mined chain remains secure.
http://bitcoin.stackexchange.com/questions/273/how-does-merged-mining-work

Aah, that makes sense 
Thank you for the link!