When you select any cell in a Numbers table, it activates the column and row reference tabs.
Clicking any column's reference tab selects that whole column.
If you then scroll to the right and shift-click on a second column, the second column and ALL columns between it and the first are added to the selection.
Clicking once on cell F6 selects that cell AND shows the reference tabs.

Clicking the reference tab for column A selects all of column A

With column A selected, a shift-click of the tab for column V (Press and hold shift, click V, release mouse button, release shift) adds columns B to V to the selection.

This is a general feature in Numbers (and other software on the Mac).
A click selects a single item.
A command-click adds a second item to the selection (or removes that item from the selection if it was already a part of that selection).
A shift click adds the item clicked AND all items between that item and the initial selection.
Regards,
Barry