Like the Division of Motor Vehicles has different regulations, manuals, tests, certifications and the like for different classes of vehicles (cars, trucks, rental cars and trucks, busses, etc), Part 135 defines the regulations, manuals, tests and certifications concerning air charter (on demand flights) and commuter operations. Any person desiring the full set of these regulations can google Part 135 on the internet and quickly find an FAR site that will enable them to read it in its entirety.
There is a different “Part” for each type of aircraft – private planes, commercial planes, training planes, LSA’s E-LSA’s, etc. Although there are different “Parts”, the level and thoroughness of safety levels is always very stringent. And, as different facets of the aviation industry emerge, different “Parts” will find themselves becoming part of the regulatory world as well.