Learning to play an RPG can be daunting and complicated. Luckily, most game companies want to encourage people to play and often put the basic rules on their websites.
Since there are tons of RPGs and Dungeons & Dragons is one of the most popular systems, we'll focus on that. But we'll also include as much information about other systems as possible to help you get started.
Roleplaying games are collaborative storytelling.
Each player makes a character, and each character has a race (like human, elf, dwarf, etc.) and a class (such as bard, fighter, rogue, etc.). The players then take their characters through the game, and their actions and decisions depend on their personality, background, class, etc.
The role of the DM is to guide the players through the world.
The DM describes what players see, hear, and smell and what is happening around them. Their job is to set up situation to which players can respond by making decisions. DMs usually work from official campaign books, which describe towns, non-player characters, monsters, adventures, and all sorts of things players can encounter in the world. But some DMs choose to create their own setting!
Players describe what they want to do.
If the DM describes the buildings in the town, the players can decide which one they want to go into. Who they interact with and what they want to do is up to the players. But the success or failure of certain actions, especially ones taken in combat, depends on rolling the dice!
Dice in RPGs can be daunting because you use more than the usual six-sided die. If you don't have physical dice, you can use an online roller, like this one at DNDDicReoller.com or this one from Wizards of the Coast.
Most dice are referred to as D + the number of sides. For example, the D4 has 4 sides with numbers ranging from 1 to 4. When playing an RPG, you'll also use the following dice: D6, D8, D10, D12, D20 (the most commonly used die), and sometimes a D100.
And check out the video below for a short introduction to polyhedral dice.
Check out these other articles on how to get started playing D&D: