Punch is an enchantment in Minecraft for the bow that increases the recoil effect of an arrow when attacking a player or creature, much like the recoil enchantment for melee weapons. It does not increase the damage of the bow.
More information about the Punch enchantment
The Punch enchantment will push the player or creature backwards more than usual.
You can add the punch enchantment to any bow using an enchantment table, anvil, or game control. Then use the enchanted bow in battle and watch as your enemies are knocked backwards by the arrow!
The maximum level for the Punch enchantment is level 2. This means you can enchant a bow with up to Punch II. The higher the level, the more powerful the enchantment. For each level, Punch adds 3 blocks of distance to the base recoil. The effect caps at 255, if commands are used.