A buffer is a reclassification based on distance:  classification of within/without a given proximity. 

•  Buffering involves measuring distance outward in directions from an object.  Buffering can be done on all three types of vector data: point, line, area.  The resulting buffer is a polygon file.
•  Most often buffers are measured in uniform distance. For example, creating a 50′ buffer around all rivers.  A buffer based on different distances is called a variable buffer.  For example, the noise level surrounding surround a street network may be based on the traffic load.  Therefore a variable buffer may be used to illustrate the noise level by using a larger distance for high traffic roads and a shorter distance for quieter roads.

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