Dice often form the basis for all RPGs so recognizing them is important. Most games use simple dice with a number on each of side. They are often referred to by D for dice, followed by the number of sides they have. A D12 is a die with 12 sides. Some games, such as the Star Wars RPG use special custom dice. This is a quick reference to the most common dice to make recognizing them much easier.
The D4 is not as common as many of the others listed here but it is used often enough to mention. Most versions of this die will use the number at the top of the pyramid for the result. Some versions, however, will place the numbers against the side meaning that whichever number is at the bottom is the result. If you’re ever confused between them look at where the numbers are focused, corner or side.
The D6 is the most common die used and will be the one beginners are most familiar with. Like most dice the number on top is the result and the die has 6 sides. Some games rely solely on these dice and use multiple of them to determine success.
The D8 is used occasionally in games like D&D. For diamond shaped dice like these the result is the one facing upward in comparison to the others. In the case of the picture the result is 8 because it is facing upward.
The D10 is most commonly used in games like Star Wars RPG and Warhammer 40k. They will often come in two varieties as shown. This is because they are often used for rolling on a chart of 100. One die represents the 10’s place while the other represents the single’s place. In the case of the picture the number would be 81. These are also sometimes referred to as percentile dice.
The D12 is mostly used in Tephra but is used moderately in other games. It, like the D20 is rather straightforward. The number on top is the result.
The D20 is second only to the D6 in popularity. It became near famous due to the popularity of D&D. The D20 system from that game has become a focal point for countless more and the die has become a symbol for the tabletop RPG genre.
Hopefully this can act as a quick reference for anyone just starting out. If there are any other dice you would like covered or mentioned let me know down below.