The Night Rating is done as part of the Commercial Pilot Licence course but can also be done as a stand-alone rating for someone just doing a PPL.

The Night Rating consists of 10 hours instrument instruction (5 of these hours may already have been done as part of the PPL) as well as not less than 5 circuits with 5 take-offs and 5 landings, a night cross-country of not less than 75nm during which 2 away landings are made and a Night Rating test.  All of these hours are dual and there is a written examination.

This rating allows you to fly in the dark but not under instrument conditions ie not in clouds or bad weather.