The visibility of each object can be turned on and off using the check boxes in the tree view, as described in Object Visibility. However, you can also hide objects by right-clicking on them and selecting Hide. The right-click menu has a title that indicates the object that will be acted upon (Wireframe in the figure that follows) so that you do not accidentally hide the wrong object.

Once an object has been hidden, you can show it again by right-clicking on the background of the Viewer and selecting Show Object: