Is there any difference between 'should' and 'must'?
In talking about rules, e.g.
You should keep quiet in the library?
Or You must keep quiet in the library?
Which one is more appropriate?
When giving rules, 'ust' expresses the obligation, but when talking about them, we often 'soften' things by using 'should', so it is possible to say 'you should keep quiet'.