Pickle is a Python-specific file format used for serializing and de-serializing Python object structures. It allows you to save the state of Python objects (like lists, dictionaries, custom classes, and even functions) to a file, and then later load them back into memory, restoring the objects to their original state. This is particularly useful for tasks like caching results of expensive computations, saving machine learning models, or persisting game states. The pickle format is binary, meaning it's not human-readable. It's important to note that pickle files can be a security risk if you load them from untrusted sources, as they can execute arbitrary code. Therefore, it's crucial to only unpickle data from sources you trust. The pickle module provides functions like pickle.dump() to serialize objects to a file and pickle.load() to deserialize objects from a file. Different pickle protocols exist, offering varying levels of efficiency and compatibility. The latest protocols are generally more efficient but may not be compatible with older Python versions.