A search on the internet brought me this description: central occlusion (centric occlusion) “occlusion of the teeth when the mandible is in centric relation to the maxilla, with full occlusal surface contact of the upper and lower teeth in habitual occlusion.” https://medical-dictionary.thefreedictionary.com/centric+occlusion

Read the other 2 definitions to understand the differences. That’s what I did.

It’s the surface of an incisor tooth facing the tongue and where it touches teeth next to it.
It’s a description of the gaps between the teeth. (In this case upper 2 and upper 3)