If this feature is enabled, you can restrict the users from accessing the platform without login. The Customer will get an option to login at the home page once logged in, then only he access the rest of the forum. Follow the steps to enable it:-

1. Go to the Settings -> Customers -> Customer Settings
2. Scroll down to the Customer login restriction and will allow it.
3. It will ask customers to sign-up or login first before going to the listing page.