Modem Routers - need advice UK

HI
I am looking at the latest 802.11ac Modem Routers) which appear mostly to be routers.

Can somebody tell me, the major differences between having a router versus a modem router?

I currently have a 82 G Belkin modem router.

Looking at the 802.11ac standard, I am thinking I may get better speeds.

Does anybody know what might be the best modem router on 802.11ac?

As info.

I have 2 PC's using Belkin adaptors, 2 laptops with in built adaptors, 2 tablets, 4 mobiles in the worst scenario.

I am living in a modern house with *** plaster board walls. 3 bedrooms. I am in the lounge and nearest to the modem router which is right by the phone line.

Thanks