Do Christians believe that the laws of the Old Testament still apply today, or did Jesus end that?

I struggle a little bit in understanding the Christian belief about the OT laws as a Muslim. One of the things that confuses me is that half of Christians say that deeds aren’t important; that salvation can only be through Jesus, believing he died on the cross for their sins. The other half believe that "works" are also essential. Which half is right? What do you think will be the fate / judgement of those Christians who preach to others that "works" isn’t important?