Backing up one database

I have a few databases created and I want to back up just one.

How do I do that?

so if my database is at

use phpadmin or command line? what is better? and how?

There is no “better”. Either method has its advantages and disadvantages. If you are used to using a GUI (graphical user interface), then phpMyAdmin is the way to go. If you are comfortable in the command line, and unfamiliar with phpMyAdmin, then use the command line.

Google is your friend here. But for CLI, I like

which is actually pretty good.

This page from the WordPress Codex:
is a bit dated, but it does provide you a few different ways, including CLI and phpMyAdmin.

If you are having trouble, it could be that the tutorial you are reading is for a different version of your software, so check that first if you run into problems.