As you likely know, you can change the width of a column in a Word table by dragging the column’s right border. When you drag the border, only the two adjacent columns are affected – one gets wider and the other narrower.
This is fine unless you have already set all your column widths and you then want to make one column narrower or wider without affecting the column to its right. In this case press and hold the Shift key before you start dragging. The only column that will be affected is the column to the left of the border you are dragging.
None of the other columns in the table will be affected but the table width will change. If you make the column narrower, the whole table will be narrower.