I think Dhouha is probably asking what kind of card he needs to buy, so as to be sure it will work with his Pi. The docs on the main site say this:
SD card size. For installation of NOOBS, the minimum recommended card size is 8GB. For image installations we recommend a minimum of 4GB; some distributions can run on much smaller cards, specifically OpenElec and Arch.
SD card class. The card class determines the sustained write speed for the card; a class 4 card will be able to write at 4MB/s, whereas a class 10 should be able to attain 10 MB/s. However it should be noted that this does not mean a class 10 card will outperform a class 4 card for general usage, because often this write speed is achieved at the cost of read speed and increased seek times.