Keepass is an open-source password manager. You can read why you should use a password-manager in
One of the biggest benefits, besides having all of my user accounts and passwords stored in one safe place, is that I do not have to think about my passwords anymore. No need to care how complicated my passwords really are.
Password managers are made to support you with the following functions:
store account information
generate passwords for accounts
open and search for existing accounts
and most important: copy and paste the values from the password manager into the web browser during the login process.
Keepass exists in several versions and for different platforms. Thus, the software in the presented screenshots or videos might look slightly different from the software version you are using. This is no big deal as most of the things are only cosmetic differences.
In case you want to access your passwords from more than one device (e.g. your computer and your smartphone) you only have to transfer the database file to your devices.
In case you add an entry on your mobile phone to the database you have keep the database files on all devices in sync.
An easy solution for this is to use a cloud storage provider (i.e. Dropbox, GoogleDrive, OneDrive you name it). Just make sure to not open the file on more than one device at the same time. Again, if you do this make sure to use a really strong master password!