A data query is a request for information from a database. It allows users to retrieve specific data by specifying certain criteria, such as filtering records or selecting particular fields. Queries are often written in a language like SQL (Structured Query Language), which is designed for managing and manipulating relational databases. Data queries can be simple, such as asking for all records from a specific date, or complex, involving multiple conditions and calculations. They are essential for data analysis, enabling users to extract meaningful insights from large datasets stored in systems like MySQL or PostgreSQL.