The organization homepage brings together your groups for administrators to manage, members to access, and possibly, prospective-members to join.
First, you need to choose a sub-domain for your organization, this will be the address of your home page (i.e. https://redwood.gaggle.email). You can also specify a description that will be displayed on your page.
Then you need to decide how your page is going to be used. If you only want existing members of your organization to access the page you can enable the "Require logged in" option. However, with this option disabled, anyone will be able to see the groups in your organization and if the online signup option is enabled for a group, they will be able to signup and join. This provides a really good way for people to discover and join your groups.