In the UK these phrases describe the main shopping centre (or road) of a town. I was wondering if their meaning is understood throughout the world and what phrases are used in other countries and regions to describe similar areas?
In the US, depending on the size of the town, downtown is a common term for the centre of town (maybe / maybe not the business district), and main street is commonly used for the primary retail road. In non-English speaking countries of course there would be local language varities, like "le centre ville" in France.
I think downtown is more common. However, in some city downtown is really downtown as in town on the low ground; it's always be uptown there too though.
a lot of cities use the actual road name of the main street to describe the main shopping street or use the name of the district. If you are writing a story and have the above phrases in it, people will know what you mean.