Subject to where you are from, different countries have different terms for "storm drain".

Based upon where you are from, different countries have different terms for "storm drain".
Accordingly to Wikipedia, a storm drain is basically a tunnel that carry runoffs (rain) from urban areas. For a layman, it helps to think along the line of sewage system that functions beneath our cities.
In the states, this is actually best known "storm drain" or "storm sewer".
In the UK, this is often called "surface water drain" or "surface water sewer".
In Australia and New Zealand, it is often called "stormwater drain".
And there you have it, when you hear someone mentioning "storm drain", "storm sewer", "surface water drain","surface water sewer" and "stormwater drain", you now know they talk about exactly the same thing.
Functions of storm drain include draining excess water (rain or storm water) and ground water from pavement, streets and carparks into rivers and streams in order to avoid flooding.
Although storm drains do a amazing job of draining excess water from the urban areas, swimming pool gratings are essentially openings where left uncovered could be a hazard to pedestrians. Left uncovered, rubbish will get into the storm drains and cause choking which can eventually cause flooding.
To ensure storm drains serve their purposes while minimizing the dangers posed to pedestrians and to prevent choking of the drains, drain covers (gratings) are widely-used to cover the inlets (openings) of the storm drains to achieve two purposes.
Over at Jonite, we specialize in steel reinforced drain covers (gratings) for your storm drains while preserving the aesthetic areas of the architecture around the drain covers.