Another Network Engineer who wants to enter Security.. Where can I Learn so I know enough to pick what security field I want to enter?

I currently have an ITPro Subscription. And I am not against doing CBT Nuggets for a month or 2 for some basic learning. (These are supplemental. And I use them to give me basic knowledge of a topic before delving deeper in various ways.)

I ask because I have been wanting to get into security for a bit, but I hit a bit of a road block where I just do not know what the fields are.

Like many of you, I assume, I can find what I need to find and teach myself when i know what I need to learn.

But when it comes to security.. All I can think to do is just watch all the things.. And that has simply not sounded enjoyable.

I need a little bit of an end goal and some paths to choose from.

To be clear I am not asking about certifying in anything. I want to KNOW and work in the field.