The colon has several functions:

To introduce items in a list

This paper investigates three aspects of the student experience: first impressions, learning support, and health and wellbeing.

To introduce an explanation

Pressure on the available services is greater than ever: the population is growing, resources are limited, and expectations are high.

To introduce a quotation

Bennett (1987) writes: ‘For Shakespeare and his age, Agincourt was a sacred time in their national history, one perhaps not approached again until the defeat of the Spanish Armada.’