A namespace is a container that holds a set of identifiers, such as names of variables, functions, and objects, allowing them to be organized and managed without conflict. By using namespaces, developers can avoid naming collisions, especially in large projects where multiple components may have similar names. In programming languages like Python, Java, and C++, namespaces help to group related code together. For example, a namespace can be used to separate the functions of a library from those of the main application, ensuring that each function can be called without ambiguity, even if they share the same name.