Well there are lots of kinds of dice, there's a D20 (D just for dice), D6, D8, D10, D12, and D4. For certain things you roll a certain number of one or two kinds of dice. It sounds complicated to tell which dice to roll for what, but it's pretty simple when you get used to it; and you do get used to it pretty fast. :bleh: The dungeon master will roll the dice sometimes, and the players will also roll for their stuff. For example of using the dice in battle:
Player 1: "I'd like to hit that Goblin in front of me" (*note: the player's character must be adjacent to the creature in order to attack. Some DMs use small figurines to get the visual of where the characters are, but others prefer to use their imagination)
DM: "Roll the D20 then."
Player 1: (it all depends on the armor class of the creature and your weapon, although weapons are not taken into account in beginner D&D. Let's say this Goblin has an AC of 7, so the player would probably need a 12 and up to hit. And then the player rolls for the damage dealt if they hit, so a D6 is the basic and most common one I know, but other classes of characters use different dice for damage.)