Hashes, especially if they are salted, are very hard to break. However, given enough computing power, it's possible, especially if it's made of dictionary words.
Passwords are not stored in plain text, so they don't know if it's 'granny123' or 'leica66'. Rather, it's deciphered into a hash, after seasoning with 'salted hash'. This is new 'alpha numerical very long digit number', is compared against what they have on file, if it's identical, then you get to login.
This long character is usually what's stolen.
The hacker can usually take a simpler route, by getting passwords stored as plain text with other more rudimentary websites that you keep a login to. Which usually is the same recycled passwords with your other banking, paypal, email passwords.
Safe practices include not using similar passwords, jumble up into non-dictionary words with upper/lower case with a mix of numbers, change often.