Reaction rates
A reaction's rate is how quickly it finishes, and surface area, temperature, concentration and a catalyst can all speed it up without changing what the reaction produces.
A worked example
A whole antacid tablet reacts in 90 seconds. Crushed to powder first, the same tablet reacts in 30 seconds, three times faster, because the powder exposes far more surface area to the water.
The mistake people actually make
A catalyst speeds up a reaction without being used up itself and without changing the products formed; it comes out the other side unchanged. A faster reaction is not a different reaction.