You should ask the seller for all the information you need about the bike, because a) they should know more than we do and b) if they can't give it to you readily then there is more risk that it is stolen. These things do happen!
Don't tell the seller this, but the name is usually written on the frame. If they can't manage that much then consider walking away.
It looks like a 2017 Giant Contend SL2 Disc: https://www.giant-bicycles.com/gb/contend-sl-2-disc-2017.
The picture is quite grainy so it's hard to be 100% sure. Check if it has the Giant Conduct disc brake system to be sure.
Here's the image in the linked product page for the 2017 Giant Contend SL2 Disc:
Looks like a nice bike - not very old because disk brakes have only been on road bikes in the last ~5 years.
The top tube profile suggests an aluminium frame not carbon fibre, and the thickness of the fork tines/legs suggest they are carbon fibre.
Both tyres are a bit low on air so pump them up before you test-ride it. And you should absolutely test ride it before buying. As long as its comfortable for you, then its a good bike.
Do note that Giant's "lifetime frame warranty" only applies to the original purchaser. Giant bikes aren't known for being counterfeited - the higher-end brands have much more of that.
When you test-ride, do a quick M check to make sure all the important parts are safe, not rattling or worn. Look at the chain and drive train's state of wear, and look at rotors for wear. You'll get an idea if its a low mileage garage queen or a worn-out commuter with tens of thousands of km on it.