View > Frame Layout affects the number of windows in the Viewing Area. The same object appears in every window, but usually with a different perspective in each window.
View > Frame Layout > One - the default; one
large Viewing Area.
View > Frame Layout > Two Vertical - two windows;
with the main Viewing Area split vertically.
View > Frame Layout > Two Horizontal - two windows;
with the main Viewing Area split horizontally.
View > Frame Layout > Three Large Top - three
windows; with the largest at the top.
View > Frame Layout > Three Large Bottom - three
windows; with the largest at the bottom.
View > Frame Layout > Three Large Left - three
windows; with the largest at the left side.
View > Frame Layout > Three Large Right - three
windows; with the largest at the right side.
View > Frame Layout > Four - four windows; with
the main Viewing Area split horizontally and vertically.