How do passwords and usernames work and how are they encrypted?

A username is an account set up by a computer administrator. An administrator has full access of the data stored and can do such things as add or remove software. A username is good because it allows multiple people to use the same computer but at the same time restricting access if desired. PassWords are group of characters that are encrypted to prevent or slow down access to unwanted users. Most PC user do not have the software like ophcrack to hack and obtain passWords.