Executable files are computer files that contain a program capable of being run by the operating system. These files typically have extensions like .exe for Windows, .app for macOS, or .out for Linux. When opened, they instruct the computer to perform specific tasks, such as launching applications or installing software. These files are essential for running software applications and can be created using programming languages like .C or .Java. However, executable files can also pose security risks, as malicious versions may contain viruses or malware. Therefore, it's important to only run executable files from trusted sources.