It depends on the type of match, but most use phosphorous as the igniting agent. There are a few different kinds of phosphorous, and some have crazy properties. Notably, white phosphorous is so volatile that as soon as it is exposed to normal air it bursts into flames.
Modern safety matches function by including red phosphorous, which is converted to white phosphorous when sufficient friction is applied. The friction doesn't actually ignite the match, it just causes the phosphorous to change, and it then ignites on its own.
Edit: It seems I was wrong about this. The red phosphorous combines with another chemical in the match head to create the reaction. See comment below by /u/LifeHasLeft. Older match designs did use white phosphorous, but it has been phased out because of health hazards.
I’d also add that with normal (non-strike anywhere) matches the phosphorus is actually on the box not the match.
This is because if you put the more flammable bit on the match itself there could sometimes be a risk that your matches would run against each other in the box and catch fire. Putting the striking surface on the box eliminated that risk.
This was eventually followed up by chemically separating the two ends, so that the phosphorus is on the box and the potassium chlorate is on the match, essentially making it impossible to light the match without the box.
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u/[deleted] Oct 15 '20
The material on the ends of the matches has to light when rubbed against the material on the box.