Chemical reactions can be sped up by adding a catalyst. The catalyst can be another chemical, liquid or heat. As an example,if you add water to nitric acid, that causes a tremendously fast reaction and can actually explode. Thats an example of a catalyst (in this case water). Please don't try this at home, though! It's extremely dangerous!
The resultant reaction is a chemical reaction that makes the acid react much more quickly.
I use small amounts of nitric acid to etch plastic integrated circuits in my company. When you heat the parts before putting on a drop of acid, the reaction to the acid is much faster and stronger. In that case, the catalyst is heat.