A serializer is a tool or process that converts data structures or objects into a format that can be easily stored or transmitted. This is often done to facilitate communication between different systems or to save data in a file. Common formats used for serialization include JSON, XML, and YAML. In programming, serializers are essential for tasks like sending data over the internet or saving it to a database. They help ensure that complex data types, such as lists or dictionaries, can be transformed into a simple string format that can be easily reconstructed later.