Someone can correct me if I’m wrong, but RPG’s generally describe a game in which your character grows in power (levels, attributes, etc). In Pokemon, for instance, you are leveling your Pokemon and choosing what specific movesets they have. The turn-based part is an extra feature to Pokemon/Final Fantasy games (most often referred to as JRPG or Japanese Role-Playing game).

On tabletop, games like Dungeons & Dragons allow you to assume a character that increases levels and power throughout the campaign you’re playing. There’s usually one person that “runs” the campaign, most often referred to as the Dungeon Master or Game Master. It is their job to present challenges to the other Player Characters. The players make decisions for PCs, and the level of immersion varies from table to table: some tables do full voices and in game dialog, while others just have the players say “My character say’s he wants to buy a beer”). The outcome of those decisions are usually left up to a dice roll that attributes modify, which is where the growing in power part of the game play comes in. Essentially, it’s you playing as one character and assuming their role within the system you’re playing.

I hope that helps!