Object vs Component Mode
Maya 2012 Tutorial
How to Understand Object Mode and Component 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, go to the front view and marquee select the eight vertices that define the object center. Five of the vertices are hidden, yet do become selected.
Click the Scale Tool and scale the vertices to reshape the cube.
Component/Object Mode Shortcut
Press F8 to quickly toggle between Component Mode and Object Mode. Another quick way to switch between object mode. faces. edges, vertices, etc is to right-click the object and choose a mode (object, face, etc.).
Pick Walking Vertices
While you are in the Component Mode - Vertices you can select a point, then press the left, right up and down arrows to select adjoining vertices.
Nudging Faces, Edges and Vertices
By pressing and holding Opt (PC - Alt) plus the up, down, left and right arrows you can nudge vertices, faces and edges. This trick is view dependent so you will get different transformations based on the selected view.
Toggling Between Vertices, Edges and Faces
With an object selected, press F9, F10 and F11 to toggle between vertices, edges and faces for your object. To better see your faces, press the 5 key to see the object in Smooth Shade mode.