What does the "h" "k" and "(5.2.2.02,6)" mean in Dibenzo(h,k)-4-oxatricyclo(5.2.2.02,6)undec-8,10- diene-3, 5-dione
The systematic (but not necessarily preferred) name tricyclo[5.2.2.02,6]undecane describes the structure of octahydro-1⁠H-4,7-ethanoindene (see this answer on how to name tricyclo compounds):



Expanding the name from tricyclo[5.2.2.02,6]undecane to 4-oxatricyclo[5.2.2.02,6]undec-8,10-diene-3,5-dione adds the functional groups, which leads to the structure of 3a,4,7,7a-tetrahydro-4,7-etheno-2-benzofuran-1,3-dione:



According to the current version of Nomenclature of Organic Chemistry – IUPAC Recommendations and Preferred Names 2013 (Blue Book), isomers of fused polycyclic ring systems are distinguished by lettering each peripheral side of the parent component using the italic letters a, b, c, etc., beginning with a for the side numbered ‘1,2’, b for ‘2,3’, etc.
For example:

        

Accordingly, fusion of two benzene rings to the above-mentioned parent structure 4-oxatricyclo[5.2.2.02,6]undec-8,10-diene-3,5-dione at the relevant sides yields the name dibenzo[h,k]-4-oxatricyclo[5.2.2.02,6]undec-8,10-diene-3,5-dione.
(Note that this name does not necessarily correspond to the preferred IUPAC nomenclature and notation.)