If you want to generate a 20-character random alphanumeric password run the following in a terminal window:
LC_CTYPE=C LC_ALL=C tr -dc "a-zA-Z0-9-_\$\?" < /dev/urandom | head -c 22; echo
Leetspeak, also known as eleet, is a alphabet that is used mostly on the internet. It uses various combinations of ASCII characters to replace Latinate letters. e.g. 3l33t