In one sense, empty things lack essence, which means that there is no intrinsic quality that makes a thing what it is.
In another sense, empty things lack independence, which means that a thing does not exist on its own, apart from conditions, relations or cognition.
A great deal of what one studies in the emptiness teachings demonstrates the relations between these two senses, and heightens one's sensitivity to their ramifications.
When you meditate on emptiness, what you actually look for is inherent existence. Instead of finding inherent existence, you will find the lack of inherent existence. This lack itself is emptiness." Greg Goode