Big Data repositories contain the following types of data:
Structured: a data collection in a well-defined format with pre-set parameters. This data type is easy to store, collect, and process.
Unstructured: a collection of heterogeneous data with no predefined format. This data type is challenging to derive value from.
Semi-structured: a combination of both structured and unstructured data. Hence, it brings together some characteristics of structured data but contains information that does not apply to relational databases.