The Selection tab of the modeling ribbon provides a variety of specialized tools for making sub-object selections. For example, you can select concave or convex areas, sub-objects that face the viewpoint, or point in a certain direction, and more.
You can use the right-click menu Panels submenu to make the available on the Selection tab, which you can then use to access and change sub-object levels. You can also use the right-click menu to add the to the Selection tab.
The general selection panels comprise the Select panel for selecting sub-objects based on certain topologies; the Stored Selections panel for saving, restoring, and combining sub-object selections; and the Selection Sets panel for copying and pasting named sub-object selection sets.
The Select By panels provide a variety of methods for making sub-object selections procedurally. For example, you can use By Surface to select concave or convex areas of a model, or By Pivot to select the outer areas of a model.