Cadets is a weekly Sunday event where master raiders Silver & Cara train people with the commonly used tactics for all raids currently available in game. These are the hard mode tactics that are usually used for guild raids, and will stand you in good stead for most pugging opportunities, and give you a solid basis for a raiding career.
Make sure to read Silver's full post about the Cadets as it explains everything you need to know:
Play in our Wookie Olympics this Sunday Afternoon@13:00 BST ~ 3 Stages: Healer, Tank & DPS ~ Take part in 1, 2 or all 3 ~ Over 20 million credits in prizes for top 3 of each stage + Chance Cubes
That moment when the link to the patch notes is almost longer than the actual patch notes