Good question OP, because it pays to have a clue what people mean when they say certain things, and I've discovered a lot of things are taken the wrong way because of those differences. So yes, I'd say semantics definitely. And therefore it pays to give more information on specifics if you're going to advise 'punishment' or such. And I think it's important, in situations like this forum, to at least understand the formal, proper meanings of terms.
I do understand people use those terms loosely, to mean different things, but just like... laminitis/founder for eg, I think of them as pretty much interchangeable. With a background including behavioural psychology, I like to stick to formal definitions.
So... punishment means a consequence that happens at the time of(or at worst, immediately after) a behaviour, in order to weaken that behaviour, make it less likely to occur in future. So, to use mslady's eg above, yes, sticking your finger in a fan - or a horse touching an electric fence, say - is indeed an eg of effective self punishment.
People also use the term 'reward' loosely too. For eg they use it to mean release of 'pressure', cessation of Bad Stuff(negative reinforcement) and they use it to mean a pat on the neck or a 'good boy' which is not a Good Thing of itself for the horse, but just a signal that *if paired* with something desirable often enough can come to mean something to the horse. And they use it to mean giving the horse a treat after everything is finished, when they put the horse away or 'just because'. Whereas I use reward and positive reinforcement interchangeably - it formally means the addition of a Good consequence - something desirable to the horse - at the time of(or immediately following) a behaviour in order to strengthen it, make it more likely to be repeated.
Here are the behavioural definitions of the 'four quadrants'...
Positive Reinforcement(+R) = The addition of something desirable in order to strengthen a response/behaviour.
Negative Reinforcement(-R) = The subtraction of something UNdesirable in order to strengthen a response/behaviour.
Positive Punishment(+P) = The addition of something UNdesirable in order to weaken a response/behaviour.
Negative Punishment(-P) = The subtraction of something desirable in order to weaken a response/behaviour.