Semi-structured data refers to information that does not reside in a traditional relational database structure but still has some organizational properties that make it easier to analyze, such as XML, JSON, or other self-describing structures. The ARRAY data type allows for the storage of a collection of elements in a single field, which is useful for containing data that can vary in size and structure. The VARIANT data type is specifically designed to store semi-structured data efficiently, and it supports different types of data formats such as JSON, XML, and Avro, making it highly versatile for this purpose.