Enzymes are specific to substrates as they have an active site which only allow certain substrates to bind to the active site. This is due to the shape of the active site and any other substrates cannot bind to the active site.
there is a model which is well known in the biology field of the lock and key model. this is because you have to have the correct key to insert it into the lock. this goes the same as an enzymes active site and the substrate.
Enzymes are protein molecules which serve as catalysts for chemical reactions.
A catalyst is a substance which will decrease the activation energy for a reaction.
So why is this important? Enzymes will make reactions occur much more easily, quickly and more efficiently than they ever would without the enzyme.
Here is a video of an enzyme demonstration I like to share with my students. The video shows how an enzyme present in our saliva (spit) can aid in the process of digestion by acting on starches present in the foods we eat.