Help About Dedivated Server/SeedBox/Dediboxes

Hello,
im very interested in buying Dedivated Server but i need more info...i got alot of stuff tha i dont know and i hope you guys can help me out get everything in place...
so...this are the Q :-)

1. What's the difference between a Dedivated Server to a SeedBox to a Dediboxes, cuz when you search it on google some companies call it a "Dedivated Server" and some "SeedBox" im very confused.

2. What is the best company to buy from...(im thinking on "LeaseWeb")

3. I saw that when you come to purchase a server i got to choose an OS...what do you think is the best...? (i never used linux so how hard it will be to learn just for this purpose??)

4. If ill buy now 1 the company got to know for what im using it for...so..they dont care ??

5. And what the deal with "Fedora Server" "Debian or ubuntu servers" ?? thats only in linux ?? if i buy windows i dont get this ??

I know its alot but im in a real problem here guys....plz help me out here :-)
Thanks.