Look at the top four cards of your library. You may reveal a creature card and/or a land card from among them and put the revealed cards into your hand. Put the rest on the bottom of your library in any order.
You may reveal a creature card, or you may reveal a land card, or you may reveal both a creature card and a land card.
If one of the cards is Dryad Arbor (a creature land card), you may reveal Dryad Arbor and another land card or Dryad Arbor and another creature card.