For all practical purposes they are the same, although I think many people would say 'close' is a more polite word than 'shut'. Why? I don't know, maybe because of association with the impolite phrase "Shut up."
The precise difference is that closing is about the action of closing, like a door may be in the process of closing but not closed yet.
A light switch, by comparison, moves so quickly that it is either on or off. We probably don't talk about the time it is changing. So we say 'shut off the light' because 'shut' is about the finished state of being closed. (An electrical engineer might talk about closing an electrical circuit, but that's technical language people don't normally use.)
'closed up' and 'shut up' mean the same, for instance a store that is closed up or shut up.