Escalator etiquette is the etiquette of using escalators: in many places, there is a convention that people should stand on one particular side of an escalator to allow other people to walk on the other side.
A 2015 experiment by Transport for London has suggested that such a convention sometimes reduces the efficiency of escalators: the number of people carried can increase if people stand on both sides.
Escalator etiquette Wikipedia
The first escalators installed in the London Underground at Earl's Court station used the design patented by Charles Seeberger. These did not let the passengers dismount in the direction of travel, as currently. Instead, a diagonal partition shunted them off to one side while the stairs disappeared under the partition. The side chosen for disembarkation was the left hand side and this is the origin of their convention that riders should stand on the right, so that the walking riders would not have to cut into a standing line of people to exit.
In certain countries, for instance Australia, Japan, and New Zealand, riders stand on the left and walk on the right, following the road rules. However, in some countries, such as Belgium, it's the other way around.