What is the difference between Grid Lines and Cell Borders?

Hey, Patrick... I feel your pain. Or, at least, your confusion.

The grid lines vs cell borders thing is logical, but very unclear in Numbers' interface, but this info might help:

• Grid lines are not conceptual, they are actual lines. What they look like is defined by a table's Style definition. Most (hmm, maybe all) of the built-in styles use gray grid lines. Whether they are displayed in the table body, and/or for header/footer cells is controlled by the settings in the Table pane of Format Inspector.
• Cell borders always trump grid lines, they're an overlay - a different layer, so to speak. If you apply cell borders, and then turn off grid lines, the grid lines turn off - but the cell borders remain. This is more obvious when you've applied cell borders to just a section of the table, and you see all the grid lines switch off but the section with cell borders remains.
• Here's the mistake we all make at first: Change your mind about having those borders, and you choose No Borders in the Cell pane of the Inspector. And, where are the grid lines? Gone! Yikes! Well, but you formatted those selected cells for *no borders* and Cell Border formatting trumps the grid lines, so Numbers is doing what it's told: giving you No Borders (which is treated as a format overlay on your grid lines). You must choose "Default Style" from the Border menu in Cell pane to return the selected cells to showing their grid lines. Yeah, because it's clear as mud that this refers to the table's style (see bullet 1), and not to some cell-border style you've created in the Cell pane.

Sure hope this clears it up for you, because when I started working with these border issues I kept finding new wrinkles, and I truly hope I have them all ironed out by now.

the grid lines are there to show the divisions between cells. Borders reside on these divisions. Grid lines rare only shown when a table is active.

The default table has a grey color for the cell borders. Grid lines are always there but actually are not visible (that is they are conceptual) and are only visible when you place a border on a cell. In most cases the tables have some color applied.

There are 4 to 5 steps to set/change the border of one, or more, cell(s):

1) select the cell(s) you want to change

2) select the type of border from the pop-up menu (no-border is an option)

3) if you did NOT select "No Border" choose the line weight

4) if you did NOT select "No Border" choose the line color

5) now choose the edge of the selection to which you want to apply the selections (make sure this is the last step)

my item (5) is the LAST thing you click after making the previous selections. It says "do all that stuff" to the borders I am clicking. if your cells already have a border then you will only see a change if you change the selections for items 1 - 4 then click which borders to apply those changes.

select a range of cells, then select "line type", then, black, then weight = 1

now click all borders

all borders of the selected cells should have a black border

now change the type to "No border",

now click all borders

all borders of the selected cells should disappear

When I hover over these items I get this:

and this:

so to me these are shortcuts to quickly modify row and column borders in the body of the table (buttons on the left) or in the headers (buttons on the right)

You can post feedback to Apple using the menu item "Numbers > Provide Numbers Feedback"