What can cell margins useful for

It is the distance between cell content and cell border is called cell margin.

Explanation:

In other words, it is called cell spacing which can be found while creating tables

Basically just setting cell margin so that content in each cell is fixed.

It is also called as cell padding in web pages also. It a just space control between cells. At the same time it not space controls between the edge of cell content.

We can increase or decrease cell space s in ms-excel.