At right is the "Symbols Window" with icons for fill (bucket), line (pen), symbols (pushpin), fonts, colors (paintbrush), and palette manager (to save & load various settings). The symbols window is where you can change shading, line widths, font sizes, etc. You can get this to pop up with Ctrl-P or Window; Show Symbol Window.

Themes in ArcView (left hand column when a view is visible) can be turned on or off.  "Active" means the box next to the theme is checked. "Selected" means it has the raised box.  At left is the theme list, with all themes active and the "Landstat.shp" theme both selected and in edit mode (it has the dashed line around the checkbox).