A zone of a specified distance drawn around a geographic feature, used to identify areas or features within that distance.
Buffering is one of the most common spatial analysis operations. You specify a distance, and the GIS draws a zone of that distance around a point, line, or polygon. Any features that fall within the buffer zone are considered "nearby" for the purpose of the analysis.
Example: A city wants to notify residents within 500 metres of a proposed construction site. A GIS analyst creates a 500-metre buffer around the site boundary, then queries the address dataset to find all properties within that buffer. Those addresses receive notification letters.
Buffers can be fixed (the same distance on all sides) or variable (different distances based on an attribute, such as noise level). They are used in environmental impact assessment, service area analysis, and proximity studies.