A claim is a request by the insured to be indemnified by the insurer following a financial loss.
A loss is the occurrence of the insured event such as fire which results in a financial disadvantage of the insured.
A loss event might arise but this may not necessarily translate to a claim because the loss event may be excluded by the policy terms, or certain laid down conditions may have not been met. A claim can be made without the insured loss event happening. In such case, the claim would be invalid.