Marshalling and unmarshalling are crucial operations in Go for encoding and decoding data, particularly when working with JSON, which is prevalent in web development. The process involves converting data between Go types and JSON format using the `encoding/json` package, allowing developers to handle data easily within their applications. By defining structs with appropriate field tags, such as `json`, Go facilitates the mapping of JSON properties to struct fields. Error handling is also essential during these conversions to ensure reliable data processing. Additionally, Go provides efficient methods for handling I/O operations, enabling direct encoding and decoding with standard output. Understanding these concepts enhances the ability to manipulate data structures in Go effectively, whether for API interactions or data storage.