What is wardriving?

I seen the movie Wardriver. It was pretty cool, though I feel like it was made intentionally to be sort of fake.

I googled wardriving and its an entirely different thing from what the movie was about. Its just guys doing analysis of signals around town. What is this? Like I googled this seems like a legal thing to do. Catching public signals like pokemon

Could somebody clarify what the hell the wardriving is? Not gonna do it myself though super curious what the hell this is