Simple past: Action happened in the past, which doesn't happen anymore.
Present perfect: Action started in the past and still holds good.
Simple past: John broke the glass. (John might have broken the glass yesterday, which is replaced now) (The object does not hold good any more)
Present perfect: John has broken the glass. (John broke the glass yesterday and it still remains broken) (i.e, not replaced yet with a new one) (Here the action still holds good)
PS. This is the best explanation I was able to come up with.
Any explanation on this by a teacher would be very helpful.