What Linux is

The word "Linux" means the kernel, the program that manages hardware, memory, and processes. The kernel alone is useless for work. It needs utilities, a shell, a package manager. That bundle is packaged into a distribution. Ubuntu, Fedora, Debian, Arch are different distributions around the same kernel.

Between you and the system sits the shell, a program that reads the line you typed and runs a program for it. On many distributions that is bash by default. The terminal and the shell are different things: the terminal is the window, the shell is the program inside it.

Run three commands to see what the system reports:

$ uname -r
6.8.0-31-generic
$ echo $SHELL
/bin/bash
$ whoami
student

uname -r