In short it means Java had a problem with the connection and therefore reset it effectively kicking you off a server (or stopping you from joining). Just simply try to re-join.
Buy ,minecraft
It sounds like you've got the client but haven't registered a premium account yet, which you need to do on the Minecraft website.
You'd be better off to solve that problem looking up what Minecraft is instead of asking here how you can show him that you understand. Just make him ask you "What is Minecraft". Then of course you explain to him by showing him you know what it is. And of course you can always play a game of it with him.
Modloader is a soon to be obsolete mod that helps solve mod conflicts, helping you install multiple mods at once.
Simply go into 'edit profile' on the launcher and select which version you want to play in. This should solve the 'outdated client' issue.
MINECRAFT!!!!
It's called Minecraft... creepers have ALWAYS been in Minecraft.
100% minecraft
Yes, its very possible. Especially if you are downloading mods/plug-ins. For example, some mods require you to delete original minecraft folders. So if you don't know what you are doing when installing a mod or something, try looking it up on YouTube first for tutorial, because if you ruin your Minecraft folder, you may just have to delete your minecraft and reinstall. In some instances, you can just click "option" at login, and hit force update, and that'll solve whatever problem you have.
minecraft is dogwater
You can email Minecraft if you have any questions about Minecraft. That's what the Minecraft Help Email is.