Ground fire - Spreads slowly through organic debri and duff, usually staying small. Surface fire - Burns small trees, shrubs, and grass. Crown fire - Extreme heat and intensity. Goes from tree top to tree top at high speeds only if conditions are right. The three things just mentioned are different fires that happen in a forest.
Every fire needs fuel, heat, and oxygen.
Take away one of these components and the fire will die. Add one component and the fire will intensify. Like in a crown fire the heat is so intense that trees, in some cases, will explode. This happens because the moisture in the tree evaporates and the heat in the tree causes it to explode into flames. Also, fire brands and ash get blown up into the sky where they land on the forest floor and cause another fire.