Mount Linux filesystem not defined in etc/fstab

Hello, is there a way to mount a filesystem which is not defined in the etc/fstab ? Could someone share me any code or command

Yes, you can use the mount command.

Here is a simple example:

mount /dev/sdb1  /mnt/data

Check out your Linux man pages for mount .

So, mount <filesystem name> <mount name> is the command
Am I right?

You are close although your nomenclature could be discussed. man pages are a very valuable source of information. man mount :

 mount [-fnrsvw] [-t fstype] [-o options] device dir