Light, sound, electromagnetic energy types, alongside gravity, are not tangible. So something can be physical without being tangible. Actually, the most of the physical forms in universe are not tangible. Tangibility was emerged in the later stages of universal evolution.
"Concept", however, is a pure human invention and only works for human psyche. Universe can and do exist quite independent from concepts; yet humans -or any other thing- can not exist without universal physical forces.
If you are still desperate for further "definition(s)" for terms that you are curious about such as "gravity", "tangible", "physics" and "concept"; you can start with entering them on Wikipedia.