Unknown things appearing on terminal after installation

[Reimu]

To run a command as administrator (user "root"), use "sudo ".
See "man sudo_root" for details.

reimu@reimu-Aspire-E5-575G:~$ user "root"

Command 'user' not found, did you mean:

command 'users' from deb coreutils (8.30-3ubuntu2)
command 'userv' from deb userv (1.2.0)
command 'fuser' from deb psmisc (23.3-1)
command 'iuser' from deb ipmiutil (3.1.5-1)

Try: sudo apt install

reimu@reimu-Aspire-E5-575G:~$

I don't understand what to do next

[Reimu]

I looked at other articles, it seems that this is just something like instruction teaching on the terminal.

[Aravisian]

It's like riding a bike. Looks so daunting at first until you get the hang of it...
Then it seems so easy once you are rolling along.