From Developer's Website:
Live for Speed is a serious racing simulator. No arcade modes, no steering aids - YOU have to do the driving. It is therefore highly recommended to drive the sim with a steering wheel, because even though you can use keyboard and/or mouse, a wheel is what you use in a real car, so a wheel should be used in a serious racing simulator. Especially when going online, where fast reactions are required.
In Live for Speed S2 you can race alone or against the AI, but the real fun is to be found online, in multiplayer mode. Racing against real people is simply the best thing and LFS makes it easy for you to do so. There are also several online racing leagues you can take part in, if you are looking for something with a more competitive edge.
A serious simulator obviously requires a very good physics simulation to provide the thrill and fun of real racing. This is done by simulating all aspects that are important to racing. LFS S2 is the second step towards our vision of what the sim must become and already does a very good job in simulating real racing. Many racing aspects are covered - comprehensive setup possibilities, fuel usage, tyre wear, a lot of different surface types, intriguing racing environments, different car classes, etc. All these aspects make sure you have enough to practise with and spend time on learning the flow of the tracks. Additionally, don't forget to plan your pitstops - find out how much fuel your car uses on a track and how are your tyres behaving on any track, with your driving style. All aspects you will have to think about in real racing and as such you need to think about them in LfS S2 as well.