How do I get to the Command Line? - The Greatest Question Ever Neglected.

First of all, sorry for neglecting to answer this question until now. I mean really sorry as I was personally stumped by this question when I was first starting out. Hopefully, this makes it easier for people just starting out with server admin work.
As I mention in the video, here are the referral links to the services I use and can recommend.:
Linode ($100 over 60 days - I get $25 later if you continue to be a customer)
www.linode.com/?r=af5a2cb6806...
DigitalOcean ($100 over 60 days - I get $25 later if you continue to be a customer)
m.do.co/c/d29698cd6a8d
Vultr ($100 over 14 days - I get $35 later if you continue to be a customer)
www.vultr.com/?ref=9026602-8H

[@ThsilPortal]

Hello. I wish you a healthy and happy life. Your interesting explanation helps me a lot.

[@Wise-Cat]

Great to hear! And thanks so much for the well wishes.

[@ThsilPortal]

can I give some questions? How many cpu and RAM should I choose to set up moodle where 5000 students can take exams at the same time?

[@Wise-Cat]

This is a difficult question to answer because what is needed depends on many factors. First, how "same time" is it? Even small gaps between access times can change the answer considerably. Second, what kinds of questions are in the exams? Some questions take more power than others. Third, assuming you're talking about the quiz module, how often is autosave of attempts set to?
Probably the best (though rather complex) way to test this would be to make a jmeter test and stress test the server with 5,000 requests going through a quiz module. If you have that capability, that will get you a much more accurate answer than the rest of what I'm about to write here.
Assuming standard multiple-choice quizzes with autosave disabled, you could probably get away with say 8GB of RAM and 4vCPUs. This also assumes that the 5,000 requests will be at least a little staggered. Though technically unable to serve all 5,000 at the same instant, in reality the wait times for each request should be fairly limited and so all requests will probably be OK. Note however, that the PHP pool settings and the SQL max_connections settings will definitely need tuning to make this work as the defaults are set extremely low to protect the server (safety first). So, I'd guess (aand it is a guess) that you could get by on an (GB offering from say Linode, Vultr or DigitalOcean etc, but the server would definitely need to be carefully setup to make it work. If this is a one-time deal, consider perhaps getting a Linode 8G and resizing up to 16G for the exam and taking it back down afterwards to cut costs.
For any more than 5,000 you'll probably start needing multiple servers with Load Balancing etc to ensure availability. Things get crazy complicated then.
Hope this helps