How to Use

I am a new hacker in the Hack the Box community,
can anyone just teach me the basics?
what are machines?

Machines/boxes are computers that are hackable.
You hack the machine with the goal of getting a remote shell on the machine (which grants you control over it). After you have a remote shell, you can read a text file that has a hash that proves you hacked the machine, which you can submit to earn points.
I suggest you start by doing the retired machines while following writeups and then trying the easy machines on the active machines.
Good luck!