TTRPG is real people meeting together and one person becomes what is called Dungeon Master. Each TTRPG is different just like RPG are different. The only difference is how you play it. In RPG you can play alone but this does not work well in TTRPG because you cant become Dungeon Master and the player, many board games have this same requirement like Monopoly, Game of Life, Twister, chess, etc. RPG can be done with the computer which lets people play the game whenever they want unlike board games that require setting it up and planning to meet.

That this the difference between TTRPG and RPG