In Plants vs. Zombies Adventures, the zombies walk through paths to enter player's buildings or RV. The player needs to place paths in the town in order to make the building available for use or purchase. All paths cost Zombucks and do not have any special effect. There are many other paths on Road Trip which are not sold in the store.
None of the paths have any effect on the zombies or the game, so it is advised to buy the cheapest path.