How do you name a bicyclo compound with a fused benzene ring?
Beside systematic nomenclature about organic structures, there are other systems in use.  One of them is the by Hantzsch and Widman which departs from a number of stem structures.  Some of these archetypical motifs are named systematically, others (still) retain their traditional name which does say little  to you about the structure (e.g., pyridine) until you learn them.  One (incomplete) compilation of these names, for example, is this one.
This being said, you either look up, or over time (i.e., training) recognize that the parent structure of your molecule is indene:

except that the double bond in the five-membered ring of the structure you showed is completely saturated.
You remember reactions on benzene, and recall about the importance to denote the sites in organic structures.  The approach to use numbers equally exists for larger compounds, too; a few positions are labeled.  While there are cases where you may shorten 1H-indene to indene, this no longer is the case to describe unambiguously the compound shown by you, which is 2,3-dihydro-1H-indene.