It is likely that your agent used the word bound instead of bonded. If this is the case then the auto insurance agent was indicating that the policy you obtained was bound, meaning coverage then took effect on the date and time the application was signed.
Agents have the authority to bind insurance coverage over the phone. After the coverage is bound, the insured has a limited amount of time to sign the application and/or pay the premium. The time limit may vary from company to company. If you, the insured, does not pay the premium or sign the application, the coverage is void from the date of inception, i.e. there is no coverage at all.
So, the coverage starts from the date the agent bound the coverage but if the policy is not signed or paid for within the required time limit, the coverage is retro-activity terminated.
Many insurance agents also required this as a binder. Then general definition of an insurance binder is a temporary insurance contract that provides proof of coverage until you receive a permanent policy. However, the definition and point of actual coverage is different for every state and also different for each policy.
Typically an insurance binder is immediate insurance coverage that can be in oral or written form. The binder's purpose is to provide temporary insurance coverage for a specified time until a formal policy is accepted or denied.
A binder or bound policy is issued by an agent to the customer, so if you need to know more information then you should contact your agent to explain about your coverages and when they went into effect.