Enzymes are proteins that speed up the chemical reactions in your body. They are a biological catalyst that lower the activation energy needed for a reaction to begin. One common use of enzymes is in digestion. You have enzymes in your saliva that help to break down compounds in foods more quicky. Enzymes function to help the bonds of molecules break more easily. Enzymes are very specific to the type of molecules they are working on. A substrate will attach to the active site on an enzyme and the enzyme will turn the substrate into products.
Example: Maltose is broken down by enzymes into your body to glucose. It is easier for your body to use and process glucose.