Whats the difference?

I think it is because a receiver also contains a tuner whereas an amp doesn't.

An AV receiver manages all of the inputs (HDMI, component, composite, optical etc etc. And outputs them to the Speakers and/or TV as appropriate. They usually have an FM tuner built in.

I have one of these and jolly nice it is too if not bang up to date Yamaha Electronics UK Ltd

Basically it acts as a hub for all of your audio, video and games console devices.

AV receiver - Wikipedia, the free encyclopedia

The difference between an amp and receiver is that the latter has a radio tuner built in.

I think it is because a receiver also contains a tuner whereas an amp doesn't.

Yup.

Over 5 years ago, some multichannel amplifiers would do all the home cinema formats at that time (multichannel mpeg, dolby digital, dts) and also catered for a few video loops and 2ch stereo inputs but didn't have a radio built in.

Nowadays, they all have the radio built in pretty much.