It is a roadworthiness check. Anything that leads to the car being unsafe.
The basics are lights, wipers, horn, indicators, tyres, brakes and handbrake.
If you take it there and it's a simple fix, like a globe or handbrake adjustment, the mechanic will likely do that on the spot. Anything that needs a bit more TLC (time, labour, coin) they'll tell you to get it done and bring it back.
Anything else that influences the safety of the car will be checked as well, such as suspension and steering. This includes CV joints, ball joints, any play in the hubs, play in the steering wheel/steering box and associated linkages.
Any obvious leaks are another thing you can get picked up on, same with holes or leaks in the exhaust. An exhaust tip, I doubt they will grab it and shake it but you know, if it falls off and damages my car - I get out and damage the driver. Get it fixed for the sake of community mindedness.
Different states have different rules. I'm in NSW and I'm restoring a car. Full nut and bolt job. *sigh* I'm documenting everything because the car will need to go over the pits for a full inspection and due to some modifications to the suspension components, will need an engineers certificate. My avatar is a pic of the motor and transmission which is best described as having the subtleties of a flying sledgehammer. I built the engine myself.