In Erlang, modules are containers that group related functions, data, and attributes together. A module is a unit of code organization and encapsulation, allowing for modular and organized development of Erlang programs. Modules provide a way to define reusable code components and separate concerns within a system.

Here are the key aspects of modules in Erlang :

1. Definition : A module is defined using the `module` attribute at the beginning of an Erlang source file. The module attribute specifies the name of the module, which must match the filename. For example, a module named `my_module` should be defined in a file named `my_module.erl`.

2. Exported Functions : Modules define a set of functions that can be accessed and used by other modules. By using the `export` attribute, specific functions within a module are marked as "exported," indicating that they are intended to be used by other parts of the system.

3. Internal Functions : Modules can also contain internal functions that are only accessible within the module itself. These internal functions are not exported and are intended for internal use or helper functions within the module.

4. Attributes : Modules can include various attributes that provide additional information about the module, such as its version, author, and description. These attributes are used for documentation, code analysis, and other purposes. 5. Namespacing : Modules serve as a mechanism for namespacing in Erlang. Functions defined within a module have a module prefix, allowing for unique naming and avoiding conflicts with functions in other modules.

6. Code Organization : Modules enable the organization of code into logical units. Related functions and data can be grouped within a module, improving code readability, maintainability, and modularity.

7. Code Reuse : Modules promote code reuse and modularity. Modules can be imported and used by other modules, allowing for the reuse of functions and code components across the system.

8. Code Compilation : Erlang modules need to be compiled before they can be used. The Erlang compiler compiles each module into bytecode, which is executed by the Erlang virtual machine (BEAM).

9. Code Dependency : Modules can depend on other modules by including them in the code using the `import` attribute. Importing a module allows access to its functions without explicitly qualifying them with the module name.