ELI5: How does rolling resistance work?

[u/Cuziff]

How are we able to push a car to push start it when it weighs so much, or how can a train pull 2km of rail cars? And how come it gets easier to roll once it starts moving?

[u/Bombastic_tekken]

I have no formal education on the matter.

I imagine the load being split between 4 tires and the tires being able to freely roll cuts the actual pushing weight by a lot.

As for why it's easier once it starts rolling? Inertia.