Is mining something specific of Bitcoin? I am very new to the world of cryptocurrencies (I first read deeply about them today) and I've just discovered the concept of mining. Everything that I've read so far applies to Bitcoin but I know that there are a lot of different cryptocurrencies. So I was wondering if mining also exists for other currencies.

Is mining something specific of bitcoin or is it possible to mine different cryptocurrencies? If so, is the process different than the one used to mine bitcoins?
Earlier cryptocurrency systems (which predated Botcoin) relied on a central clearinghouse to prevent fraudulent transactions, such as double-spending.  One of the objectives of Bitcoin was decentralization.  To prevent double-spending without a central clearninghouse, blocks of transactions need to be mined.  The process of mining requires a significant amount of computational effort to be expended by the miner.  Other nodes on the network will not recognize a mined block of transactions without this proof of work.