Here's what you need to know about Braavos:
* A powerful Free City: Braavos is one of the nine Free Cities, independent from the Seven Kingdoms of Westeros. It's known for its vast wealth, powerful navy, and influential Iron Bank.
* A city of mystery: Braavos is shrouded in mystery, with its origins and inner workings being largely unknown. It's said to have been founded by escaped slaves from Valyria, and its culture is distinctly different from Westeros.
* Home to the Iron Bank: The Iron Bank of Braavos is the most powerful financial institution in the known world. It loans money to various kingdoms and individuals, often wielding significant influence over their affairs.
* A training ground for assassins: Braavos is home to the Faceless Men, a secretive guild of assassins who train individuals to become skilled killers and masters of disguise.
So, when you see "Bravos" in the books, it's referring to this mysterious and powerful city.