This is Random Blocks, a survival/PvP minigame!
You can select up to 24 different blocks, and choose out of 4 teams.
Every game, a giant bedrock box is randomly filled with the blocks you have chosen, and everyone is dropped in the arena with their team members.
Objective: Kill your enemies!
Craft tools, weapons and armor!
Enchant!
Find your enemies!
Kill them!
Win the game!