You can select from these modes, which span their fields of effect as follows:
A depiction of the Fields’ effects can be seen here.
Use this setting to define the radius around object points or polygon surfaces within which the Field effect strength fall off from 1 to 0.
If Mode is set to Surface, this setting defines if the effect should be maintained up to the radius or if it should be clipped at the surface while ignoring the Radius setting:
This function is often required for spaces that have an inside and an outside. This is entirely logical for the shape Fields (e.g., Spherical Field) but less obvious for particle, spline and volume objects, etc. Volume objects often have settings such as radius, with which a space can also be placed around a point or they define the space themselves. There is always in inside and an outside. This function defines how the inside should be treated. If nothing should happen (option enabled) or should null values, for example, be applied (option disabled), which will hide Fields below it if Blending Mode is set to Normal.