Obstacles are a way to slow down attackers while towers and troops do more damage. They can only be placed on the pathway itself. They work best in combination with towers.
There are two types of blockages, the Barricade and the Blockade. The barricade is basically a cheaper alternative to the blockade. Both stop attackers (except for werewolves) from advancing but allow defending troops to move over them. They work best in front of towers to slow people down.
Spikes are clearly visible and attack every unit that walk over it. Some units, such as Frosters, hover over the trap and are not affected by its damage. Spikes can be attacked by some troops, while others will ignore them.
The Jester Box on the other hand is invisible until it gets triggered by the hero. It deals its damage in one explosion to units within range. It cannot be destroyed.