So if I take gas money from a friend on a trip am I a chauffeur?
If your friend asks you to take him somewhere, and he offers you a couple of dollars for gas, that's okay.
If you mention that you're going somewhere, and your friend asks to ride with you and offers gas money, that's okay too.
If you register to use an app that says, "I'll take anyone anywhere they want to go for $X," then you're soliciting for fares, which is generally regarded as a commercial activity. Depending on your location, you may need a commercial driver's license and/or commercial registration and insurance on your vehicle.
In most jurisdictions, you need insurance. The type of insurance may vary depending on how and where you drive your vehicle.