Shield Power
From OGame Wiki
Shield power measures the damage that a combat unit can absorb each round until the structure of the unit is damaged. The actual shield strength of a ship in combat is calculated with the following formula:
[edit] Special Cases
If the firing ship's attack power has less than 1% of the defending ship's shield power, the shot is deflected by the shields in case they have not been shot down by heavier ship types. Example: A Light Fighter has 50 Attack Power, while a Death Star has 50,000 Shield Power. Thus the Light Fighter's attack power is 0.1% of the Death Star's shield power, and therefore the Light Fighter's shots at the Death Star will be deflected.
This is known as the Bouncing Effect.