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The region is essentially what is call “selection” in some other applications – it is the text that you have selected, or, in Emacs jargon, the text that you have marked.
The cursor (not the mouse pointer) defines the position of point, which is one end of the region. The other end is the mark. The mark is invisible; the point is indicated by the cursor.
You can set point by clicking ‘mouse-1’ or using the arrow keys. You can set the mark in any of these ways:
‘C-SPC’ or `C-@’ (point stays put; point = mark, for now)‘mouse-1’ (point’s old value becomes the mark)‘mouse-3’ (clicked position becomes point; point’s old value becomes the mark)Each buffer has its own region (it has its own point and mark). There is always a region in any given buffer, as soon as there is a mark there. By default, the region is not highlighted, because having some text always highlighting would be annoying.
active region: If you use TransientMarkMode, the region is highlighted whenever it is active; it is not highlighted, otherwise. You can make the region active (and highlight it) at any time by using ‘C-x C-x’ (‘exchange-point-and-mark’), which swaps point and mark.
The region is also made active (and highlighted) whenever you define it using the mouse (even if you do not use Transient Mark mode).
Some commands act differently when the region is active. Typically, their scope of action is limited to the active region.
SecondarySelection – yes, Emacs has a second selection. Very handy.