This is the ultimate learning experience for an Apex Legends player! You will play for two hours (or more, according to the options selected) with two pros for your Hardcore Coaching service in Battle Royale or Arenas, and in the meanwhile, a third pro will watch you as you are playing. Therefore, he can guide you further as the other two coachers are helping you through the game.
This service usually grants you Rank Points on the way, especially if you win a lot!