The Selection Region flyout gives you five different ways to select objects within a particular area or volume. Clicking and holding on the Selection Region button opens a flyout containing the Rectangle, Circular, Fence, Lasso, and Paint Selection Region buttons, from top to bottom.
Selection Region flyout
For the first four methods, you can select either objects that are completely within the selection region (window method), or objects that are within or touched by the selection shape (crossing method). Toggle between the window and crossing selection methods by using the Window/Crossing toggle on the main toolbar.
To select using a region (general method):
To cancel the selection, right-click before you release the mouse.
Selects objects within a rectangular area.
Selects objects within a circular area.
Selects objects within an irregular “fence” shape.
Selects objects within a complex or irregular region with a single mouse action.
Lets you select objects by dragging the mouse over them.