Guidance for people in Wales to protect themselves from coronavirus has been updated to make it compulsory for face masks to be worn in shops and indoor spaces.
They should also be worn in other public settings when social distancing is not possible.
Wales' health minister said face masks may reduce transmission from one person to another if made, worn, handled and removed or disposed of properly.
The First Minister made face coverings mandatory on public transport, including taxis, in Wales, from 27 July.
He said the decision was made due to the fact the economy is getting "back into operation" meaning more people will need to use public transport.
"Mandatory face coverings is one of the range of mitigating measures we have introduced with operators in train and bus services in Wales", Mr Drakeford said.
Face coverings have been mandatory on public transport in England since 15 June.
Mr Drakeford added, "Our roads and train tracks cross the order with England. Having separate regimes is not sustainable in the long run."
So, what is a three-layer face covering and how does it protect someone from transmitting the virus?
There are many different types of masks that can be bought or handmade.
New research has recently identified the following preferable types of fabrics, number of layers and the composition of a non-medical, fabric mask.
an inner layer of absorbent material such as cotton
a middle layer of non-woven material such as polypropylene
an outer layer of non-absorbent material, such as polyester or polyester blend
To be effective the masks should cover the nose, mouth, and chin and be secured with elastic loops or ties, include multiple layers, be washable and reusable.
If a fabric mask is not dirty or wet and it is reused, it should be put in a clean plastic, resealable bag.
Fabric masks should be washed in soap or detergent and preferably hot water (at least 60 degrees) at least once a day.
WHO says "the widespread use of masks everywhere is not supported by high-quality scientific evidence, and there are potential benefits and harms to consider."
The World Health Organisation urges people not to wear a mask:
if it looks damaged
it is too lose
do not wear it under the nose
do not wear a mask if it difficult to breathe through
What other masks are there?
Medical masks - also known as surgical masks -are made from a minimum of three layers of synthetic nonwoven materials, and configured to have filtration layers sandwiched in the middle.
WHO advises that these should only be worn by health workers, anyone with symptoms of Covid-19, people caring for suspected or confirmed cases, people aged over 60 and people with underlying health conditions.
There are also respirators which are specifically designed for healthcare workers who provide care to COVID-19 patients in settings and areas where aerosol generating procedures are undertaken. Healthcare workers should be fit tested before using a respirator to ensure that they are wearing the correct size.