Insurer refers to entities providing financial safety against potential future losses or damages. If your house catches fire, the insurer helps cover the costs to repair or rebuild it.
Pro Tip 2/3
Context Specific
The term 'insurer' is specific to the context of insurance and doesn't apply to other forms of security. An insurer won't help if you lock yourself out, that's a job for a locksmith.
Pro Tip 3/3
Risk Assessment
Insurers assess the risk of insuring someone and may deny coverage if the risk is too high. The insurer refused to cover the old factory, citing its weak structure as a high risk.