If you already own it, download the client software: minecraft.net
If you don't own it, you need to create an account, and you need to pay for it. The PC version costs: $26.95
If you want to set up your own Minecraft server, you can download the server file from https://minecraft.net/en-us/download/server.
Texture packs are also known as resource packs.
You can always purchase a hosting service to set up your own Minecraft server from the likes of MCPRO Hosting or many other services like that, but you can just set up your own on a good computer at home for others to connect to if you wish.
You can download the server file from: https://minecraft.net/en-us/download/server
After you download the file, you can run it using this command line:
java -Xmx1024M -Xms1024M -jar minecraft_server.1.11.2.jar nogui
If you need the user interface, take out the “nogui” part from the command line.
You can get more information about how to set up a Minecraft server at the Minecraft Wiki.
If you wish to run snapshots, the best way to find and download the latest snapshot is to go to Minecraft News. There look for the news about the latest snapshot. Once you get to the appropriate page, you'll find the jar file download for the respective snapshot.
You can give a player unbreakable items by using the following command:
/give (yourname) minecraft:diamond_pickaxe 1 0 {Unbreakable:1}
In this example, you are giving an unbreakable diamond pickaxe