Stealth -
The semantic explanation, in brief, is this:
if you stand in front of a mirror and raise your right hand, your reflection raises its left hand. This is the reversal I was talking about.
However, if you imagine a line that bisects you from head to foot, dividing your right side from your left side, you would call everything to the left of that line 'the left', and everything to the right of that line, 'the right'.
If you then imagined that line not just bisecting you but bisecting everything around you, it would also bisect the person in the mirror - you have divided everything you see in half. Therefore everything in front of you would be either left or right - including the hands belonging to the person in the mirror.
So objects are not, in fact, reversed at all. If you raise your right hand, it goes up on the right-hand-side of that invisible line. And the person in the mirror also raises the hand on the right-hand-side of the line.
The reason it appears a reversal is simply that we are used to thinking of the question of 'right side' and 'left side' as being viewed from the inside, so that you imagine the person in the mirror is carrying around with them the same conception of right versus left as you - and that therefore their left hand was raised - when actually, it was the hand on the right.
I can't remember where I read that, but it would've been explained a lot better. It's not just about semantics but about a really internal way we model the world by sort of viewing everything as being centred on ourselves. It was very interesting. If I can find it I'll post it because I suspect all the above has just confused things still further 