The term "uptown" and "downtown" are just used to separate areas of a particular community into two depending on some factors. These terms actually originated from New York City, and are widely used in American English.
In their origination, the more populated part of the city that has more commercial enterprise was usually referred to as the downtown, also called Lower Manhattan. Any parts or areas that are higher than this region toward its north were referred to as uptown or upper Manhattan.
In its modern geographical context, any part of the south a person describing can be the downtown, while towards the northern part can be described as an uptown. Also, in terms of the vertical height of a particular location, the lower part, usually closed to the river, is usually referred to as the downtown, while the upper locations are often referred to as uptown.