theres only two types of tv lcd and plasma "not led"
led is the way the picture is lit up from behind
most popular sets are now lcd led the other is lcd using florescent tube(s the older standard type) but just a good and cheaper
in other words buy an lcd tv
plasma are not as popular and are more expensive. you'll not go wrong with samsung or lg, get built in freeview hd as well
Sue have a look at this link. It's the John Lewis TV Buying Guide and tells you all you need to know. Look at their LED TVs, the staff are incredibly knowledgeable and helpful and you get a 5 year guarantee for free on all their TVs. I am looking at the Samsung LEDs at the moment. I'm nothing to do with JL by he way.
I've just bought a new LED TV and am very happy with it. LED is cheaper to run (approx 40% more efficient apparently) but as the screens are thinner the speakers are quite weak. Not a problem if you have a home cinema set-up but worth bearing in mind if you don't.
Just bought a Samsung 40" Led smart Tv from Comet and am very pleased with it. Good picture and even the sound isn't too bad for such a slim Tv. It can even be connected to the internet.
I endorse ladybirder's comment about John Lewis - by far the best place to buy your new TV and it comes with an included 5-year warranty and the best after-sales service you'll find. Panasonic is my choice, btw. (Don't forget that Comet is an "iffy" retailer at the moment).