Keychain Access is a tool that Mac’s have it is a very handy tool for it you forget a password that is stored in your computer or web browser. It is the place where all passwords are saved so if you want to delete a password data because the computer has become a shared computer or you aren’t wanting that information saved in the keychain access you need to open the tool up to access those details and remove them.
Located in your applications folder is Keychain access, once you have opened that go to your top menu and select keychain and preferences. This will bring up the option to be able to reset default keychain, which will allow you to create all new passwords.
If you forget your password to your accounts this allows you to retrieve the passwords without having to scribble them down on a piece of paper you could misplace. Macs store passwords for you, and in some cases it will automatically fill them in when needed. This though isn’t a recommend option if your Mac or account is shared. It also stores user names, websites, servers, Wi-Fi and networks passwords. Of course its safe to do as you have the control in telling your Mac whether you want your password and user names stored into the Mac’s keychain.
So before you reset passwords for your accounts check your keychain access as it stores that information for you.