A way to classify theology

I'm now fully embarked on Historical Theology by Gregg R. Allison. I find it to be a very good book because it doesn't have a trace of "I'm a hot shot scholar and this is my big work" but is just a solid rendition of historical theology, and it feels complete. It has 33 chapters, so I'm just going from chapter to chapter straight through. I've already learned a lot in the first two chapters which encourages me to read it all.

But in the first chapter he has a useful chart, which I can't replicate here obviously, showing the relationship of all the types of theology. There are five: historical theology, exegetical theology, biblical theology, systematic theology, and practical theology.

Exegetical and biblical theology really are the foundational work that becomes systematic theology, so I can include them in 'systematic theology.'

So if you want to get a complete understanding of theology you learn systematic theology. Then you learn historical theology (which is not foundational to systematic theology, the Bible is foundational to systematic theology, but it is how each doctrine developed in time and thus gives a grounding of sorts to systematic theology).

Then, the mysterious practical theology. Practical theology is just what it sounds like. Practical doing. Spiritual formation. This is where the ideas, practices, and goals of the Work reside. It is also where other schools, mystical schools, Eastern Orthodox ways, etc. reside. Spiritual warfare resides in practical theology. Etc.

So see it like this:

Historical Theology > Systematic Theology > Practical Theology

This helps to see in perspective where the Work resides vis-a-vis Christianity in general.