Most people create a number of usernames passwords for various things like banking and online shopping.
Usually people will create one or two common usernames and password and use them for pretty much everything they do online. While this makes remembering them easier it also means if the account is compromised someone could possibly access other accounts of yours.
Other people will try to create a different username and password for each account but this of course becomes very difficult to keep track of. Luckily most browsers like Google Chrome have a built password manager that does a pretty good job but sometimes it will miss an account or two.
KeePass is a free to use password safe that can manage ever password you ever make. Once downloaded and installed you create a master key and if you wish you can also require the use of a password file or link your windows account. Once you have logged in you will notice a great directory structure down the left side that lets you add groups and then create entries under those groups. This makes it very easy to separate your email and banking account if you wish.
All you need to remember is that master key which I would recommend be a fairly long and complex password and you will have access to all the usernames and password you ever make. As long as you remember to update KeePass after making new ones. I would recommend installing KeePass on a second machine and syncing over the database file so that in the event your computer is completely destroyed you will still have access to KeePass.
Check out the link to download KeePass: