Cardinals
In short
The Cardinals are a professional baseball team based in St. Louis, Missouri, competing in Major League Baseball.
In plain words
They are a famous sports team that plays games with bats and balls. They play their home matches at a large stadium in St. Louis.
A simple example
A fan wearing a red cap and cheering at Busch Stadium is supporting the Cardinals.
Why it matters
The team has a very long history and has won many championship titles. They are a major part of the culture and identity in the city of St. Louis.
Easy to mix up
Do not confuse them with the Arizona Cardinals, which is an American football team.