Access modifiers are keywords used in programming to set the visibility of classes, methods, and variables. They determine how and where these elements can be accessed within the code. Common access modifiers include public, private, and protected. Each modifier serves a specific purpose, helping to encapsulate data and protect it from unauthorized access. Using access modifiers enhances code security and maintainability. For example, private members can only be accessed within the same class, preventing external interference. In contrast, public members are accessible from anywhere in the program, allowing for broader interaction. This controlled access helps developers manage complexity in their applications.