Text (6th/7th+errata): Search your library for a basic land card and put that card onto the battlefield. Then shuffle your library. [Oracle 2009/07/08]
Can get a Snow-Covered land. [Duelist Magazine #6, Page 132]
You do not have to find a basic land card if you do not want to. See Rule 701.14. [D'Angelo 2001/07/14]