In order to process buying and selling of Cryptocurrencies, a user has to broadcast his/her transaction on the whole network (that must be recorded in a Blockchain). The process of successful recording a transaction is known as Cryptocurrency Mining.
Like generation of Bitcoins, Cryptocurrency Mining includes two steps: Adding transactions to Blockchains (for securing & verifying) and releasing a new currency. The basic elements a user needs, to step into mining is PC (specialized or consumer hardware), and combination of graphic cards and CPU.
Learn in detail about Cryptocurrency Mining here & here!