system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:How do airplanes, as they're leaving the gates, move backwards without the tug-cars?

Also, how do they slowly move forwards - is it the result of thrust from the jet engines or is there power being generated which is physically linked to the wheels?
gpt
Very few aircraft backup without tugs anymore. Some use their thrust reversers (very carefully) but this is becoming rare. 

When going slowly forward ("taxiing") it's just low thrust from the engines, nothing is driving the wheels. Once you get moving, idle is usually fine to roll along.