Most of the operating systems for Raspberry Pi have default password for accessing the Raspberry Pi.

In Raspberry Pi OS, the default username is pi and the default password is raspbian. Now, everybody using a Raspberry is knows this is the default password. So when you hookup your raspberry to the internet or network anyone can open up your rapsberry, well... you will have to open SSH. You don't want that! You want your Raspberry to be secure! So change that password!!

Changing the password of your Raspberry Pi

To change a password of the current user in Raspberry Pi, execute the passwd command:

pi@raspberrypi:~ $ passwd
Changing password for pi.
Current password: 
New password: 
Retype new password: 
passwd: password updated successfully

Do understand that you have to be logged in a the Pi user.

you want to change a password of another user, you can run the passwd command, as follows:

$ sudo passwd <USERNAME>

So if you are logged in as a different user than Pi and you want to change the password of pi do:

pi@raspberrypi:~ $ sudo passwd root
New password: 
Retype new password: 
passwd: password updated successfully

That's all folks!

Happy programming!