Is it an actual physical sensation, or some kind of nervous reaction? Is it a physical event, or just a brain response to tell us we’re injured or damaged?
What I want to know is: when you take a painkiller, is it suppressing the pain itself, or is it supressing your receptors in that the pain still exists, you just can’t feel it?
I’m not sure if I explained that well…
Pain is the reaction of specualised nerve cells to stimuli which can/does cause tissue damage.
According to this page (despite the cutesy layout):
“Pain is Nature’s way of telling you you are still alive!”
– Master Chief ‘Jack’ Urgayle, G.I. Jane
[sub]I think.[/sub]
That’s a bit like the old question whether there’s a sound if a lonely tree falls down in a forest unheard by anyone. The feeling of pain is the reaction of the brain to signals coming in from the nerves that there’s something wrong, which can injure you; the reason why nature put it that way obviously is to warn you, so you do something to prevent damage. If you take painkillers, you don’t feel the pain any more, but the thing that caused your pain (and might injure you) is still there (that’s why people who cannot feel pain are not necessarily advantaged compared to “normal” people, as one might think).
I think that might be simplifying it a bit too much. I like Ice Wolf’s answer.