Back in bygone days, there was the 4 nations rugby competition, held between England, Ireland, Scotland and Wales. The team which won the annual contest was awarded the Triple Crown.
The 4 nations became the 5, with the inclusion of the French, and more recently, the 6 Nations, including the Italians.
So, there is a 6 Nations championship, where you can be Champions (if you finish top of the league), or you can be Grand Slam winners (if you beat everyone else), but there is still the Triple Crown, the mini contest between the original 4. Whichever of these 4 teams does best against the others of the 4 nations then wins the Triple Crown.
And that is what happened on Saturday.