Mall Insurance is used to preserve Items and Skills that were bought from the Item Mall NPCs (Including Reward Points). This is used specifically for a case were you are “perma-killed” (killed). The items will be received, on any other character in your account preserving them. This lasts for only a limited time. (If your character died just before purchase, the insurance will not recover the items lost.)
This Insurance last for 3 months.
A nice helpful tip is to always have another character in the account that has their entire inventory empty.