Partial Selection

[puzzledpaul]

In addition to the above, I think it's worth mentioning other nuances of using the A key.

If you have a 'stable' selection - ie elements that remain 'highlighted' when you remove the cursor from them - and use A, then wings will centralise the selection.

If, however - you 'hover' cursor over a specific chunk of geometry ... whether that chunk is selected or not ... and irrespective of whether it is v/e/f/b ... wings will place this temporarily highlighted portion / element in screen centre ... ignoring whatever else is selected.

So what, I hear from the back row

Well, for a start it allows you to modify large (intricate) selections easily ... without losing what's already been selected.
User selects stuff
places cursor over new area / region, presses A
user selects more stuff
etc etc

Another use is if using something like Face | Bridge ... where the faces being bridged are very small (difficult to see / select) ... and a large distance apart.
User aims at first face,selects same
Aims at second, selects ... then bridges.

If used in v mode, this gives user great precision of movement around the scene ... and can all be done / achieved without losing any selection that's present

Worth a bit of playing around with ... I suggest.

As is View | Align to selection
Select a face
V|AtS will align face parallel to screen plane ... and by doing so show user its true shape (assuming it's flat)

pp