[Defender] Is it a plug-in or a service?

Hi, some of the plug-ins like Defender, and Hummingbird are they services that you sell or stand alone plug-ins?

I would guess that Defender gets updates to blacklists and whatever else for as long as you are a member? Or is that untrue?

Some of the other plug-ins appear to be tied to services as well.
(that is not wrong in any way I would just like to understand them better)