Object vs Component Mode
Maya 8.0 Tutorial
How to Use Component Mode and Object Mode in Maya
In the Object Mode, objects are treated as a complete unit.
By selecting the object and clicking the Component Mode icon, you have access to move the object's points, lines and faces. The object components may be moved, scaled or rotated.
Component Mode works with Polygons, Nurbs, Subdivision Surfaces and Curves.
Add a CV Curve to the workspace (Create > CV Curve tool).
Select the curve and click the Component Mode icon. The icons to the right of the icon allow you to select various components of the object.
With the Vertices icon selected, choose the Move tool and move the vertices to reshape the curve.
Add a polygon cube to the workspace. In the cube options set the Divisions to two in all directions. Select the cube and choose the Component Mode. Once again the icons to the right of the Component Mode icon allow you to select specific object components.
Select the Face icon. Using the Move, Scale and Rotate tools, you can alter the face.
Select the Vertices icon. Using the Select tool (q key), go to the front view and marquee select the eight vertices that define the object center. The five hidden vertices are also selected.
Click the Scale tool and scale the vertices to reshape the cube.