Places are a form of location in the Virtual Environment. Locations are the key factor of a Virtual Reality--everything must exist somewhere. It is possible for a location to be a location itself, such as a box which can hold something and also be located in a room or on a patio.
Places have more information than the rudimentary Location. They are generally not located Locations, but instead represent a physical area in the Virtual Environment, such as a room in a building or a sidewalk outside of a building. They also define Pathways to other Places, Realms and environment conditions.
Realms are a form of meta-place. Multiple places can be grouped into a single realm. Realms can be defined heirarchially, so you can have a building in a realm which is a district of a city, which is in the city's realm, which is in the country's realm, and so forth. The realm defines broad aspects of the Virtual Environment, such as Permissions and Environmental Conditions like Weather.
See Also: Realms, Pathways, Environmental Conditions, Permissions