An overview of neighborhood classes (arcpy.sa)

There are six neighborhood classes each of which defines a different shape or area. When a neighborhood object is defined, only the cells that have their cell centers contained within the neighborhood are actually considered to be part of the neighborhood. All tools which can take a neighborhood object do so as an optional parameter. If you do not define a neighborhood object then a default neighborhood is used.

NbrAnnulus	Defines an annulus neighborhood which is created by specifying an inner and outer circles' radii in either map units or number of cells.
NbrCircle	Defines a circle neighborhood which is created by specifying the radius in either map units or number of cells.
NbrIrregular	Defines an irregular neighborhood which is created by a kernel file.
NbrRectangle	Defines a rectangle neighborhood which is created by specifying the height and the width in either map units or number of cells.
NbrWedge	Defines a wedge neighborhood which is created by specifying a radius and two angles in either map units or number of cells.
NbrWeight	Defines a weight neighborhood which is created using a kernel file specifying the values to multiply the cell by that are within the neighborhood.

Tools that use neighborhood objects:

BlockStatisticsFocalStatisticsPointStatisticsPointDensity

Nota:

Point Statistics and Point Density only use the NbrAnnulus, NbrCircle, NbrRectangle, and NbrWedge objects.