Looking up...
On y va à pied, ça marche.
We'll walk there, that works.
To walk on foot.
Il marche vite malgré son âge.
He walks fast despite his age.
Marcher takes no preposition for distance.
To function or work (of machines, plans).
Mon téléphone ne marche plus.
My phone doesn't work anymore.
Ça marche = it works; also OK, agreed.
From Old French marchier, of Germanic origin.