Honestly, it's pretty easy. Its just playing in everyone's collective imagination with rules.

You go around the table to each player and say what you want to do and the Game Master or Dungeon Master tells you what happens based on your decisions. Sometimes you'll roll a dice based on the rules or if the DM wants to leave something up to chance, but that really is all there is to it.

Player: I want to go down this hallway.

DM: Ok, you reach the end of the hallway, it leads to a dead end but the wall looks flimsy as if its fake.

Player: I would like to try to break it down.

DM: Roll a 20 sided die

Player: I rolled a 19

DM: That's good! The goal was a 14. You easily break down the wall! But as it crumbles, there are enemies on the other side. Time for combat!

Things are little more complicated when you add all the rules and everything together but the basic rhythm is player asks, DM responds and you do that for a while. Its hard to really explain why this is fun but its very much like a video game but without limits. The wall would have to be scripted to be breakable in a video game. With Dungeons & Dragons, the wall may not have been planned to be breakable, but since the player rolled high enough it is now breakable.

I always send my new players this video. Its pretty long but Matt Colville explains the basics of the game VERY well. https://www.youtube.com/watch?v=Eo_oR7YO-Bw