A password manager is a software in which you can store all your passwords. It basically stores all your data in some file or database, and keeps that encrypted. All the passwords can be accessed be one single master password. This ensures that you just need to remember one password, and using that you can access all your passwords.
Here is a free password manager for Windows with bank-grade encryption to store passwords. It uses AES_128_CBC_SHA cipher suite for encryption.→