Regions.

In addition to a point (marked by the cursor in the current window), each buffer may contain a mark. Everything between the point and mark is called the current region. The current region typically delimits text to be manipulated by certain commands. We have set up Emacs so that the current region is shaded.

C-@

sets the mark at the current point, and pushes the previous mark on a ring of marks. If ARG is present, it instead puts the point at the current mark and pops a new mark off this ring.

C-SPC

is the same as C-@.

C-x C-x

exchanges the point and the mark.

M-@

sets the mark after the end of the next word.

M-h

sets the region (point and mark) around the current paragraph.

C-x h

sets the region (point and mark) around the entire current buffer.