Difference between US Open Cup and MLS Cup? All these soccer "cups" and "championships" confuse me. LSIQ right here
I try to explain it as this to my less cultured friends:
Imagine during baseball season if while all the leagues were being played they set aside one day a month or every couple weeks where there was a single elimination, random draw, tournament involving all MLB, AAA, AA, A teams. Every team's name is put in a hat and whoever gets pulled plays the next team pulled. So you could have a MLB team playing a single A at home or on the road, you could have two MLB teams play each other, you could have two single A teams play each other and everything in between. It's a tournament set up for Cinderellas and for the middle of the pack big teams that have no chance of winning a championship over the course of a season.
Now if you really want to get into it, these Cup competitions in Europe exist because a long time ago (1890s) there weren't enough teams to hold a league, and travel was more complicated so going on the road week in week out wasn't an option. So the cup games were less frequent and were played whenever players could show up (most of them were factory workers). Then when sports got more popular in the 20th century and they formed leagues rather than abolish the cups they kept them and set aside days when they would be played.
The MLS cup complicates things since we're American and love playoffs. While in all other countries the team on top of the standings (best record/most points) at the end of the season is the champion, in MLS they take the top whatever teams and have playoffs.