What is buffer analysis in GIS?

A buffer is a zone at a fixed distance around a point, line, or polygon, computed as new geometry. Buffers are used for proximity analysis: which objects lie within 300 meters of a rail line or sewer?

In GIS software and GeoApps, buffering is a standard geoprocessing operation. Units and projection (CRS) determine whether distances in meters are correct; on WGS84 at high latitudes, reprojection may be needed.

A buffer is not an administrative border or bbox. It is an analytical tool translating distance in space into an area or ring for further selection and overlay.