Others have covered the definition of a corn dog.
A "cron dog" however, is when you use cron to schedule a dog command, which is an updated version of the cat command installed via the moreutils package that provides additional features such as colorized output and line numbering, making it more versatile.
THIS HAS BEEN A DUMB LINUX FACT
The main difference is the additional physical gearing for 4 high and 4 low gears, both of which have different gearing than "regular" drive.
I have an older Audi with a Torsen Quattro AWD system, and an ancient Toyota 4Runner with 4WD. The 4Runner can be switched into either 4 wheel high or 4 wheel low gears to deal with different conditions. The Audi always has the same gearing, it cannot be switched.
It's like the gears on a bicycle - 4 low is the one where you barely move while standing on the pedals - maximum torque per revolution.
You can go rock crawling in a 4Runner in 4 low. You really should not go rock crawling in an Audi or Subaru without 4 low, no matter how much ground clearance the vehicle has.
The National Park Service has this rule because it doesn't want to spent time and taxpayer money rescuing people who think AWD is the same as 4WD with a low range gearbox.