What is a First or Second Order Reaction?

Rather than get into the details of enzyme kinetics, I will link you to a webpage that I think does a good job. In essence, the order of the reaction is dependent on the number of reactants and the power to which each reactant is raised.

So it’s based on the number of reactants going in?

@Iclamae Not exactly. Let me try to simplify (this is not “pure” physical chemistry, but still…). Some reactants can have a higher order than 1. For example, consider this reaction:
A + B -> C This reaction is first order with respect to A, and B, but is overall a second order reaction.

Now, the following reaction is different:
2A + B -> C is second order with respect to A, first order with respect to B, and overall is a 3rd order reaction.

ah, hrm. It’s slowly making a place in my brain. Thanks much ^_^