Hello.
There are two types of games.
1) The classic servers that you can play for free by just downloading the program: "WOM Client" from
www.minecraft.netIn this game, you choose the server you wanna play from a huge list with online servers.
Our server is: Opticraft Dev Server
2) The SMP Server(Survival Multi-Player). In order to play on this kind of servers, you have to pay 20$( I think) on
www.minecraft.net. In this program "Minecraft" you will be asked to insert an IP in order to play.
Our IP is: smp.opticraft.net
You insert it and you join immediately.
These are the two choices you have about Minecraft. You can search WIkipedia for minecraft and what it is. Once you get it, in less than 2 weeks you will know many things if not all (personal experience..
).
On the choice 1, you just build, or chat with others. There is no great interest sometimes.
On the choise 2, you can build, fix, craft, make parties, and believe me it deserves each one of the dollars it costs. The money is for life-time purchase.
On choice 1: You can buy a world through donation, a title near to your name, etc.
On choice 2: You can get many many things that are dependable to plug-ins that each server has. The server of OPticraft is not yet PvP, and I think it will not become MMO-RPG. It is a Survival server. PvP arena is under progress right now.
I hope I covered a great proportion from your questions. Anything else, you need post here.