Definitions for "All Risk Coverage"
Insurance that protects against all risks except those specifically excluded. In an all-risk policy the burden of proof that the peril causing the loss was excluded falls to the insurer. In a named peril policy the burden of proof that damage was caused by an insured peril falls to the insured.
Coverage that protects you for all losses except those specifically excluded in your policy.
When you have all-risk coverage (building or contents), you are insured for almost everything, unless it's specifically excluded from your policy (e.g. intentional damage to your own property would not be covered). This is the most common type of coverage because it offers the most protection, especially for any strange unforeseen events.