On a vehicle, what are lugs?

A lug nut is a fastener, specifically a nut, used to secure a wheel on a vehicle. Typically, lug nuts are found on automobiles, trucks.

https://en.wikipedia.org/wiki/Lug_nuts

On a bicycle, they are frame attachers.

https://en.wikipedia.org/wiki/Lug_(bicycle_part)

I'm pretty sure that on a car, the lugs are what the lug nuts attach to, holding the wheels on the car. ie: the threaded posts.

They are those things that connect battery and starter cables - the flat ends with a hole in for the bolt to go through. Sometimes on smaller wires too, but they use fancy things now on most.
https://www.waytekwire.com/products/1424/Battery-Lugs/

In some places, the term can refer to the auditory input devices attached to the overall vehicle controller (and other standby or backseat controllers).
https://en.wikipedia.org/wiki/Ear http://en.wiktionary.org/wiki/lug

lugs are also what the "gripping" tread of a tire are called.. "Lugnuts" hold the tire AND the rim onto the wheel. (just a mechanic)...

lug nuts hold the wheels of your car to the hub on your axles or in new cars your c.v. axles.