Enzymes are biological catalysts made up of proteins that facilitate chemical reactions in living systems. They can initiate or accelerate reactions essential for various biological processes. Key characteristics of enzymes include specificity, efficiency, and the ability to function under mild conditions. There are several types of enzymes, categorized based on their functions, such as hydrolases, oxidoreductases, and ligases. Understanding enzymes is crucial for grasping their role in metabolism and other biochemical pathways.