An overview of the Overlay tools
Overlay analysis tools allow you to apply weights to several inputs and combine them into a single output. The most common application for Overlay tools is suitability modeling.
There are several approaches for performing overlay analysis. Although the methods differ, they all follow the same general steps for solving a multicriteria problem.
Since each approach is based on different assumptions, the meaning of the numbers and the analysis techniques are specific to the approach. Which one to select will depend on the problem you are addressing.
The following table lists the available Overlay tools and provides a brief description of each:
Tool 
Description 

Transforms the input raster into a 0 to 1 scale, indicating the strength of a membership in a set, based on a specified fuzzification algorithm. 

Combine fuzzy membership rasters data together, based on selected overlay type. 

Overlays several rasters using a common measurement scale and weights each according to its importance. 

Overlays several rasters, multiplying each by their given weight and summing them together. 