In DnD, the amount of damage an attack does is based on the type of weapon your character is using. A few combinations of damage die are common; 1d4, 1d6, 1d8, 1d10, 1d12, 2d4, and 2d6. If you're not familiar with DnD style notation, you would read XdY as "[X] dice, each with [Y] sides," so 2d6 means "two dice, each with six sides."
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Amateur attempt to Math Nerd up some statistics below )