It is the amount of moisture needed to maintain the original form or function of contact lenses. Higher moisture content does not necessarily mean better contact lenses. If the moisture content is high, the initial fit is good, but wearing it for a long time can drain your eyes and give you dry eyes.
If the moisture content is low, the initial fit won't be as good, but it will not take away moisture, so it is good for the long-term. Using highly moisturized lenses for short-term and less moisturized for the long term is also works well.
Rather than only using contact lenses with high moisture content, it is important to find the right one considering one's wearing duration and lifestyle.