In general, a query (noun) is a question, often required to be expressed in a formal way. The word derives from the Latin quaere (the imperative form of quaerere, meaning to ask or seek). In computers, what a user of a search engine or database enters is sometimes called the query. To query (verb) means to submit a query (noun).
A database query can be either a select query or an action query. A select query is simply a data retrieval query. An action query can ask for additional operations on the data, such as insertion, updating, or deletion.
Languages used to interact with databases are called query languages, of which the Structured Query Language (SQL) is the well-known standard.