How do can i make like a Minecraft server/world and invite people on it?

So my friend and i want to get a small group of people from our high school together that play Minecraft PC and just play on a survival world together and well… I'm not sure how. I mean I've seen youtubers play on a personal servers together and i just wanted to know what to do. Please be descriptive!

… Thanks!

Just follow this guy:
I watched the tutorial and got a 20 person server (with people able to join) no problem.
Hope this helps, good luck with your server!