How do I change what is shown in the various views?
Tap the "Settings" button at the top.
But what does it mean?
There are way too many ways to interpret a chart than would be practical to implement - disregrading personal interpretation preferences, different charts would be cast for different purposes (with completely different interpretations). You should instead investigate for yourself the different philosophies and techniques used.
What House systems are supported?
Placidus, Whole Sign, Equal Sign, Porphyry, Koch, Equal Vehlow, Meridian, Midheaven, Moon, Earth, Solar, Sun, Alcibitius (Declination), Alcibitius (Semi-Arc), Arcturan, Campanus, Classical, Horizontal, Morinus, Natural Hours, Topocentric, and Regiomontanus