What does it do?:ref:

This plugin allows you to add a page header setting to enforce secure (HTTPS – SSL) or insecure (HTTP) access to a specific page. An obvious application is to protect online ordering pages, site login pages, or any other sensitive information.

Page access is configured through the TYPO3 backend on page-to-page basis using the Web >> Page module, Edit Page command, and the HTTPS Enforce (SSL) checkbox.