The government has been accused of sending out mixed messages when it comes to who has to wear a mask and when, with many calling for clearer guidance.
It may help to distinguish between masks and face coverings.
The former are worn by doctors and other healthcare professionals when interacting with patients, while the latter are for the public.
Face coverings are intended to be much more comfortable, allowing them to be worn for prolonged periods of time.
Coverings are compulsory on public transport in England, Scotland and Northern Ireland, with Wales introducing the measure on 27 July.
Shoppers already have to wear them in Scotland, which comes into play in England on 24 July. Wales and Northern Ireland are considering introducing the measure.
There are exceptions, however, with children under 11, people with breathing difficulties and anyone with a physical or mental impairment that impairs them from wearing a covering being exempt.