The ".so" file extension stands for "shared object" and is commonly used in programming, particularly in the Linux and Unix operating systems. These files contain compiled code that can be shared among multiple programs, allowing them to use the same library of functions without needing to include the code in each program individually. This helps save memory and makes updates easier, as changing the shared object file updates all programs that use it. Shared object files are typically created using C or C++ programming languages and are loaded into memory at runtime. They are similar to DLL files in Windows systems. Developers can create their own ".so" files to provide reusable code for their applications, enhancing modularity and efficiency in software development.