A "regular" shock is an emulsion shock in that the nitrogen charge is housed in the same chamber as the oil. The main difference between a "regular" shock, such as would be found on most OEM's, etc and what Fox or a racing shock company calls an emulsion is that the Fox shocks are able to be disassembled, rebuilt, and tuned via shims and the OEM is sealed from the factory and can not be modified, tuned, or rebuilt. You can also get emulsions from Fox and other companies that are machined to hold coils whereas few, if any, OEM's do that.