Posted by FantamRooster
If you can understand after reading this, you're smarter than I am. I'll think that I've grasped it, then breathe, and it falls out of my head again.
http://www.astrology-zodiac-signs.com/astrology/houses/house-systems/
Posted by HappyCapper
Mathematically, it's pretty complicated. Howard Sasportas, I think, did a good job describing different house systems (including Placidus) in his book "The Twelve Houses" if you want an overall and not too mathematical explanation. And the rest of the book is really good too, imo, so that's something I would recommend anyway, if you're interested.