Dice
GURPS uses six-sided dice only. All "success rolls," and most other rolls, require you to throw three dice ("3d") at once, add up the number of pips, and compare the total to a "target number."
To figure combat damage, and for many other things, GURPS uses the "dice+adds" system. If a weapon does "4d+2" damage, this is shorthand for "roll 4 dice and add 2 to the total." Likewise, "3d-3" means "roll 3 dice andsubtract 3 from the total."
If you see just "2d," that means "roll two dice." For instance, if an adventure says, "The base is guarded by 5d human soldiers and 2d+1 robots," that's short for, "Roll five dice for the number of human guards at the base. Then roll two dice, and add 1, for the number of robots."
For really huge numbers, dice can be multiplied. For instance, "2d×10" means "roll 2 dice and multiply by 10."