This insurance guarantees you for the damage that your “sinistres” could cause to your neighbors. Attention, only "incendie", "dégât des eaux" and "explosion" are
concerned (for the other "problems" you need a responsabilité civile).
For example, if your washing machine overflows and floods two other apartments ... (if you do not have this insurance you'll have to pay for everything ...), if your apartment burns and destroyes half the building.
Always check how much your insurer plans to repay.
Depending on the location of your home, check if you are insured against damage from natural disasters “catastrophes naturelles” (floods “inondations” in particular).