To show, hide, extract, or remove particular data from a larger set, narrowing it down, or the specific criteria used to do so. Examples include:
- only showing features that share a particular common attribute value
- removing outlier points from a Lidar point cloud, or only displaying those considered to be the ground surface as opposed to vegetation or other objects on the surface
- selecting all values in a raster above a certain threshold and exporting them to a new raster, leaving lower values as no-data or other unique value in the result
Filtering can work in either direction depending on criteria and desired result - keeping something in or excluding it from the result.