What is the difference between an informal and a courtesy crossing?

A conventional informal crossing is a place such as at a centre-of-road pedestrian refuge or at a triangular island at a traffic roundabout where pedestrians are helped to cross the road. Drivers are not expected to and seldom stop. Pedestrians simply wait for a gap in the traffic and then cross the road. Courtesy crossings are designed to encourage drivers to want to stop. Pedestrians wait until a driver has stopped and then cross safely.

Traffic splitter islands used by pedestrians compared with courtesy crossings

Traffic splitter islands are designed for the convenience of drivers not pedestrians. The presence of pedestrians at a traffic splitter island creates a distraction for drivers when they should be concentrating on the movements of other drivers.
Drivers have insufficient space to safely stop as the leave the roundabout. Pedestrians have to wait for a gap in the traffic and then attempt the dangerous act of crossing more than one lane (5.7m) of traffic entering or
leaving the roundabout. The triangular shape of the traffic splitter island is inconvenient and
uncomfortable for pedestrians.

Courtesy crossings are designed for the convenience of pedestrians as well as drivers. Drivers have time and space to stop safely and consider pedestrians separately from other drivers. Pedestrians need to cross only a single lane of traffic and so wait for only one vehicle to stop. The single lane in each direction reduces traffic speed and increases the likelihood that drivers will stop. The central refuge is designed for the maximum comfort of pedestrians.