Loss

The insurer is liable to pay for the loss in the following instances:

1.) The proximate cause of the loss is the peril insured against

2.) The immediate cause is the peril insured against, even if the proximate cause isn't the peril insured against

3.) It resulted from rescuing the insured thing from the peril insured against
4.) If it was caused by mere negligence or carelessness by the insured or his agents (if it was caused by gross negligence or recklessness, the insurer won't be liable)

In fire insurance, for instance, the insurer will be liable if the thing was destroyed by fire (proximate cause,) if the fire that destroyed the thing was caused by something else (immediate cause) or, even if it wasn't destroyed by fire, it was damaged by something else while it was being rescued from the fire. This is just an example; every insurance company will always set its own terms in the policy to establish what causes will make them liable and which ones won't.

Deductible Clause

You find this in motor vehicle insurance. The deductible clause states a fixed amount the insurer will pay in case the vehicle is damaged. It represents the contribution of the insured to the loss, making him liable to a part of it.

Franchise Clause

This is the marine insurance's equivalent of the deductible clause. It sets a minimum, not fixed, amount that the insurer will pay for the loss. If the amount of the loss is lower than the minimum set in the franchise clause, the insurer will not pay -or he will have to pay for the whole loss.

Co-insurance Clause

This also found (impliedly) in marine insurance. If the thing is insured for less than its value and a loss happens, the insurer will become a co-insured of the uninsured portion. It can also apply to fire insurance, but there must be an express stipulation to that effect.

Friendly Fire vs. Hostile Fire

In insurance, not military, terminology, friendly fire refers to a fire that burns in the place where it is expected to burn (ex. a lighted lamp.) The insurer is not liable for friendly fire.

Hostile fire is fire that burns in a place where it shouldn't be burning (ex.a lighted cigarette thrown into the mining company's explosives depot.) The insurer is liable for hostile fire. A friendly fire can become hostile if it escapes from its normal place, such as when a lighted candle gets knocked down and ends up setting fire to the tablecloth.