This random password generator is fully client-side (JavaScript) software. It means, your password is generated in your web browser, by your computer/phone (so the password does not leave your system) - in the opposite to server-side password generators, where your password is generated on a distant server (who know where, by who know who, and can be used for who know what) and it's sent to you around the world (often in an unencrypted form).
It supports custom character sets (non Latin alphabets can be used).
This tool is based on Stanford Javascript Crypto Library (SJCL) - more details: random.js