The term designates in the first place the position of an object on the earth surface by means of an explicit reference system, which is often the system of geographical coordinates. Those coordinates, essential for locating the object, represent the geometrical part of the G.I.S. It will sometimes be said that they are used to define absolute location of an object, even though any measure defining this location necessarily refers to a conventionally defined marker. The measure of absolute location is a static measure.
The notion of relative location or geographical situation is richer in that it defines position of a place with respect to that of other places of similar nature, and inside networks. The appraisal of a relative location relies on a set of measures of distance and accessibility with respect to places chosen as reference. Relative location is a dynamic notion. It must be permanently re-defined taking into account evolutions of other places considered as reference as well as of accessibilities, which are always measured within a particular space-time relation.
The term location also designates the result of the action of choosing to locate an object in a place, taking account of relative benefits that may be generated by position of the place. The actor in charge of location must answer to the following question: where ? Where to live in the case of a household faced with the choice of a residential location, where to establish production of a good or of a service in the case of a firm, where to place a collective facility in the case of public authorities while being sure that the chosen location will be the most advantageous one in view of given objectives.
In concrete terms, the reflection that precedes such a choice implies taking into account a large diversity of factors, among which some have an explicit spatial dimension. For firms, particular account will be taken of location and transport costs of (material and immaterial) resources needed for production (inputs), of location of competitors, or of location of markets and of transport costs generated by the carriage of those goods or services toward those markets. For optimal residential location, locations of work places, land costs and transport costs between home place and work place will be more particularly considered. Account may also be taken of less objective dimensions linked to spatial representations actors may have of those relative locations. However, on basis of a large number of observations, parameters that seem to systematically enter in these choices appear to be few as well as relatively stable.
A whole strand of research has developed around the problem of modelling optimal location of a firm, starting from the pioneer works of Weber (1909), about optimal location, and of Hotelling (1929), about interaction between locations. Later developments on these location issues have progressed more toward enrichment of the economic approach and of formalisation methods, than toward a renewal of modalities to take space into account. Works in the field of economic geography are proposing new research tracks in those directions.