Begin the region at the cursor C-SPACE then move the cursor around how you like, cursor keys, fwd-back word/line/sentence etc...
C-w kills the selected region and puts it in the clipboard (kill-ring)
M-w copies the selected region to the kill-ring
C-y pastes the last kill/save (cut/copy) from the kill-ring.
The kill-ring is nice, in that it's a list. M-y will paste the last item from the list, and pop it out of the list. The next M-y or C-y you do will be the next item in the kill ring, and so on...
By default Emacs doesn't do selection overwrite when you start typing on a selected region.
Of course, Emacs being Emacs, you can customize this using delete-selection-mode
Windows clipboard will be placed in the kill-ring when switching to Emacs from another windows app.