What are the browser features Norton is alerting to install?

Norton Password Manager
1

After I updated to v. 22.8.0.50 of NS, when using Firefox 49, I occasionally get a popup alert at the bottom corner of the screen that says:

Some of the Norton protection features are not installed on Firefox.

Install Now.    Remind me later.

While I realize it's likely a legit alert, it makes me uncomfortable to install something when I don't really know what "protection features" it is referring to, and whether it's reversible.

I'm using Norton Security Toolbar 2016.8.0.95 and Norton Safe Web.  I have chosen for Norton Identity Safe, Norton Home Page, and Norton Safe Search are turned off.

If I click "Install now", what happens to my Firefox browser?  What is installed?

Thanks.