Original: It was initially thought that the dark region might be a lake of a fluid or at least tar-like substance, but it is now clear that Huygens landed on the dark region, and that it is solid without any indication of liquids.
Simplified: It was at first thought that dark areas near the center of Titan could be a lake of a liquid or tar-like substance, but the probe landed on the dark area, and it is solid without any liquid.