• The match head contains an oxidising agent, potassium chlorate (KClO₃), together with easily burned substances, glue and powdered glass.
• The striking strip on the side of the box contains red phosphorus, glue and glass powder.
• When you strike a match, friction heat turns a tiny amount of red phosphorus into white phosphorus, which ignites spontaneously in air.
• This heat decomposes potassium chlorate:

KClO₃ → 2KCl + 3O₂

• The oxygen released makes the match head and the wood burn faster and more intensely.