Pickle is a Python module that is used for serializing and deserializing Python objects. Serialization is the process of converting a Python object into a binary format, which can then be saved to a file or transmitted over a network. Deserialization is the reverse process, where the binary data is converted back into a Python object.

One of the primary use cases for Pickle is in machine learning projects. When working with feature engineering, for example, it can be time-consuming to redo the process every time you start a new session. By using Pickle, you can save the feature-engineered data in a binary format and load it back later, thus saving time and increasing productivity ¹.

Additionally, Pickle allows you to store multiple objects in a single file. This means you can save various data objects together, and when reloading, you can choose to load only the specific objects you need, rather than all of them at once ³.