An item of data that is identified by an arbitrary name. The key is the name, and the value is the content; for example, the key might be CITY, and the value might be CHICAGO. A key-value database is a set of key-value pairs. Variables Are Key-Values A variable in a program is also a key-value pair that is initiated by a statement such as int counter=0, which is a C/C++ example that defines an integer named COUNTER (the key) with a value of zero. See variable, hash table, lookup table and configuration file.