This is the overview of HACS.
The overview consist of the sections you have enabled, your pending updates and important messages.
Every repository that has a pending update will show here, if you click on one of them a popup will show that give you the option to update it.
This is your gateway to the sections in HACS where you will find your installed repositories.
Here are your integrations (custom_components)
Here are your themes, and elements for lovelace.
Here are your automations apps
This opens a popup with information about HACS.