As the business grows, you want to give online access to your partners and customer so that they could view their data, communicate with you, and even transact online. For example, customers would like to see their policies, view the premium calendar, pay premium online, download payment receipts, create new cases for change requests like address changes or other such requests, track their case progress, etc. On the other side, agency staff will need to see cases and respond to them.
Behind the scenes, inside Salesforce CRM, a case should be created and the Producer linked to the customer should get the case assigned automatically. Also, Partner Accounts, Contacts, Roles, and appropriate permissions should be there for visibility of corresponding data based on staff designation and custom branding.
If you are an insurance agency vendor you will need a saas multi-tenant partner and customer portals in the Salesforce Experience cloud so that any agency using your AMS could have their own portal for their clients. They will like custom branding, their own administrator and users, and their own feature set.
If you do not use Salesforce, still the concept is the same and we can develop Partner and Customer Portals for you over any web framework of your choice in C# .NET, Python, PHP, NodeJS for example.