Definition

Identification. The situation which exists when the position indication of a particular aircraft is seen on a situation display and positively identified.

Radar contact. The situation which exists when the radar position of a particular aircraft is seen and identified on a situation display.

Source: ICAO Doc 4444 PANS-ATM

Description

The aim of identification is to unambiguously match a flight (in the air) and its representation on the situation display (a plot or a track). In other words, the controller needs to make sure which aircraft corresponds to a particular symbol on the situation display.