Structured data is data that has been organized into a formatted repository, typically a database, so that its elements can be made addressable for more effective processing and analysis.
A data structure is a kind of repository that organizes information for that purpose. In a database, for example, each field is discrete and its information can be retrieved either separately or along with data from other fields, in a variety of combinations. The power of the database is its ability to make data comprehensive, so that it yields useful information. A database query language, such as SQL (standard query language), allows a database administrator to interact with the database.
Structured data contrasts with unstructured and semi-structured data. The three can be considered to exist on a continuum, with unstructured data being the least formatted and structured data being the most formatted. Data is increasingly amenable to processing as it is increasingly structured.