By Martin Kleppmann
The geometry of a Blender scene is constructed from one or more Objects: Lamps, Curves, Surfaces, Cameras, Meshes, including, but not limited to, the basic objects described in the Section called Basic objects in the chapter called Mesh Modelling. Each object can be moved, rotated and scaled; these operations are performed in ObjectMode. For more detailed changes to the geometry, you can work on the mesh of an Object in EditMode (see the Section called EditMode in the chapter called Mesh Modelling).
After adding a basic object via SPACE>>Add menu, if the Object is a Mesh, a Curve or a Surface Blender changes into EditMode by default. You can change to ObjectMode by pressing TAB. The object's wireframe, if any, should now appear pink: That means this object is currently selected and active.
Select an object by clicking it with the RMB. Multiple objects can be selected by holding down SHIFT and clicking with the RMB. Generally, the last object to be selected becomes the active object: It appears in a lighter pink, whereas the non-active selected objects appear purple. The definition of the active object is important for various issues, including parenting.
If you click the active object while SHIFT is pressed, it is deselected. Pressing AKEY selects all objects in the scene (if none are selected previously) or deselects all (if one or more is selected previously).
BKEY activates Border select: This allows you to draw a rectangle by holding down LMB and then selects all objects that lie within or touch this rectangle. Note that Border select adds to the previous selection, so if you want to be sure to select only the contents of the rectangle, deselect all with AKEY first. Holding down SHIFT while you draw the border inverts the operation: all objects within the rectangle are deselected.