There are 8 status effects in game:

Burning
Hemorrhaging
Poisoned
Diseased
Chilled
Concussed
Sundered
Overcharged

Some of these apply a DoT of 4-6 seconds; others cause a one-time instance of direct damage and/or a debuff for 4 seconds.

Burning and poisoned, for example, are DoTs. Meanwhile, Sundered and Overcharged do initial direct hits and then apply Minor Breach and Minor Magickasteal, respectively, for four seconds.

Force of Nature counts how many are on the target and gives you 660 penetration per status effect. It does not matter who applied the effects. If all 8 status effects are active, you get 5280 pen on that target.

Unfortunately, since Force of Nature’s pen is not reflected anywhere, it is difficult to track exactly what benefit you’re receiving at any given time. I believe that’s because your pen will vary by target based on each target’s status effects, so it can’t just be added to your stat sheet. The author of Combat Metrics says it will take time to implement a stack tracker, but hopefully we can get one sooner rather than later.

For a list of each effect and how to apply it, see here:

https://en.uesp.net/wiki/Online:Combat