`std::error_code` is a class in the C++ Standard Library that represents error conditions in a portable way. It encapsulates an error code and an associated error category, allowing developers to handle errors more effectively. This class is particularly useful for functions that can fail, as it provides a standardized method to report and check for errors without using exceptions. By using `std::error_code`, programmers can easily distinguish between different types of errors and manage them accordingly. It is part of the `<system_error>` header and is commonly used in conjunction with other error handling mechanisms in C++, making it a vital tool for robust software development.