Using a password manager brings many benefits.
You only have to remember one good password--your master password.
You can use the password manager to generate randomized secure passwords for you.
Since you don’t have remember them, you can use a different password for each place you log in.
You can use the manager on virtually any device (PC, Mac, mobile phone, tablet), and it will fill your logins for you.
Not only can you store logins such as web pages, but you can store secure notes. Also, you can store notes within your logins, like answers to security questions.
You no longer have to save your logins or password insecurely, such as in your email or in a note on your cell phone.
LastPass is a good password manager with a nice free account.