This is a Game?
You probably already knew that.
People have been enjoying popular tabletop Role-Playing games, or TTRPGs, for over half a century, yet most still explain what RPGs are at the beginning of the book. As a nod to tradition, and on the off chance you're actually new to this, I'll sum it up by saying it's a set of standard rules and methods for representing the character as the "role" you'll be playing, and fairly deciding whether things they try to do will succeed.
You probably already knew that, or would figure it out pretty quickly. You didn't open this for me to waste your time, so let's get to the point — how do you do it? What are those rules?
The Short Version
Grab some dice — any common dice will do. When your character tries something, figure out how good they are by adding up your bonuses. Grab that many dice and roll 'em, and count the odd numbers. The person running the game will total up the things working against you and roll as well. If you roll better than they do you succeed by the difference.
Everything in the game works this way. If you punch the drunk in the bar, how much better you roll determines how hard you hit him. If he rolls better, he blocks and punches you!
The Rest of the Book
The resolution system is simple and standard, but "add up your bonuses" is vague, and what about damage? Initiative? Cooperative effort? Extra effort? Multiple attackers? Multiple targets?
How do I build a barbarian? An assassin? What about magic? What if I want to play a werewolf?
"The devil's in the details."
How is this game any different from a hundred others? It depends. You might think the deep end of the dice options — completely unconstrained dice — is pretty radical, but those are options.
No reason to be sketchy. Let's see what it looks like in action.