How are a catalyst and an intermediate similar? How are they different?
A catalyst speeds up the rate of a reaction by lowering the activation energy barrier which is, presumably, the energy required to achieve the reaction intermediate. Catalysts are also not consumed in the reaction, they are regenerated towards the end. A reaction intermediate is a configuration that a molecule takes prior to achieving it's lowest energy form which would signify the end of the reaction. Intermediate usually are hard to isolate because of the incentive to go to the most stable configuration. How are they different? A catalyst is not a part of the reaction product and it doesn't get consumed. An intermediate in a reaction is transformed into the product. How are they similar? Well, catalysts drive the reaction and make it easier for the reaction for follow through. Since intermediates are high energy and thermodynamics tells us that low energy is favorable, the incentive for a high energy intermediate to drive down to it's stable for can also drive a reaction. I hope that helps. I hope it makes sense.
