There are 2 servers (well 3 actually, one is a test server). First server its called International, stable server and then we have the Speed server, where everything is 3 times faster then on stable. The speed server also has some new stuff, like new troops, new spells and theese new stuff will be implemented on the stable server too. We dont know when yet, but it will be sometime in the next 1-2 months i guess. Keep in mind that when the new stuff will be implemented we'll have a server restart, so dont get too attached to your village if you play on stable.
PS Yes, your friends have to join the same server as you if you want to play together. But you can also play on both if you want.