The open() function in Python is a built-in method used for file handling, allowing users to create, read, update, and delete files. By specifying different modes ('r' for reading, 'w' for writing, 'a' for appending, and 'b' for binary), open() provides flexible ways to interact with files. Commonly used with context managers (with open(...) as file:) to ensure files are closed after operations, open() is fundamental in handling file I/O in Python, supporting applications across data processing, logging, and configuration management.