GCSE literature lets you study books/plays and you analyse them in greater depth. Language however focuses more on, slightly obviously, the language used and the purpose behind it.
whats the big/main differences between the two at gcse?
Language is when you basically just look at how language is used in different contexts, why people use language differently and analysing the effects. Plus you do some of your own writing in different styles.
Literature is when you study books/plays/poems. It's sort of like language in a way as you have to analyse the language used in the pieces sometimes, but you focus more on the plots/symbols/structure etc.