Hi lahannman,
The Type number is a code that identifies specific engine specs within a model number series. It can identify things such as engine mechanical parts, color, decals, governed speed and any OEM specific specifications. Two engines with the same model number but different type numbers may only have one part that makes them different, sometimes they will have many differences. Using the Type number is the only way to ensure that you get the correct parts for your engine.
I hope this helps,
-UtahAV
-Mark