It can go two ways depending on your preferences: use a shorter passphrase generated from a large dictionary; a good one can be obtained from 1password:
https://1password.com/txt/agwordlist.txt
https://1password.com/password-generator
or a longer passphrase from a short dictionary including only the most common words, like the EFF one:
https://secure.research.vt.edu/diceware/#eff
I don't use either generator, preferring a local command:
$ shuf --random-source /dev/urandom --head-count 5 ~/.local/share/words |
paste --serial --delimiters -
wrapped in a small helper script with desktop notifications and copy-to-clipboard.So if someone finds out your password for a certain site is `Facebook1234ABCD` they have a fair guess at every other password?
Same applies for `MyPasswordFB` using the reverse method.
So in the end the password contains numbers, letters both capped and lower case and special characters.
You just need one little website to leak passwords in plaintext and all your passwords are up for grabs.
I used to do the same thing and I stopped for that reason.