This thing.
One of the oldest trophies in hockey, and the single biggest one in the major-junior division of Canadian hockey. Nearly every province and nine US states have a team that compete for it.
As to why it’s called the Memorial Cup, it’s in memorium of all of Canada’s best and brightest across all armed forces.
Okay, but who competes for it?:
Four teams in a round robin tournament.
The Champions of the three CHL leagues: The QMJHL, the OHL, and the WHL, who win the President Cup, the J.