I don’t think that the term “West Coast” and “East Coast” is a thing in Europe…only really an east coast.
Might be somewhere else uses the same terms, like Africa or South America or Australia.
In the US, the term is important because there are two major population clusters, the larger one in the east and the smaller one in the west, with a comparatively-uninhabited area in between. It’s very common to have servers that target one or the other, to keep low latency, or people active at times appropriate to cover one coast or another.