it's a kind of sassafrass soda, sometimes with vanilla added, so it's not anything at all like ginger beer or ginger ale. but some are made with sarsparilla, and Sarsi or HeySong or other sarsparilla sodas are similar to root beer but perhaps rootbeer is sweeter. the only other soda i can think of remotely in that flavor profile is maybe Dr Pepper
When I was a kid I lived near an A&W drive-in restaurant where they'd come outside and latch a tray on to the car window and take your order(car windows were a lot sturdier back then).They served their root beer in these giant mugs that weighed a ton but it was the best root beer I've ever had.