If something is closed, access to it or through it is not possible.
Examples: My door is closed (I can't pass through it because the door is now moved to a position that is preventing access)
The shop is closed. (It is no longer open and I can't gain access to it or enter it.)
A more abstract example .... My mind is closed (I am not open to new ideas or new ideas cannot enter.)
If something is enclosed, then all of it is contained in something, or all of it is surrounded by something.
Examples: I enclosed some money in the letter. (The money is put inside a letter)
For privacy, I enclosed the front of my house yard with a hedge plant (the hedge plant fully surrounds my yard)
My fist enclosed a small toy (The fist of my hand fully wraps round the toy.)