Flood maps include a series of zones that indicate whether an area is prone to a high, moderate, or low flood risk. Flood Zone X is an area of moderate to low risk, which is a non-special flood hazard area. All this means is that the risk of flooding is reduced (compared to a special flood hazard area), but that doesn't eliminate the potential for flooding altogether.
If you live in Flood Zone X, flood insurance isn't federally required. However, you may want to purchase it, just in case a flood occurs. If you can't decide whether the flood coverage is worth the cost - or which flood zone you're in - talk to an independent insurance agent.