Q: does it mean: they have sex before marriage, drink alcohol or what? i don't get it do you? Another brilliant answer there "Rash" :)
A: Liberal or modern Muslims are Muslims who are not so strict about their religion, i.e. they don't follow it strictly by the book. They follow certain basic aspects of the religion and are generally quite nice people to get on with as they are quite relaxed (a bit like me I suppose).