In this topic, the 'selecting' term is used as 'making current'. You select the 3rd cell - you made current the 3rd cell, but you didn't highlight the content of that cell.
The 'highlighting' term is used as 'highlighting content and making current'. You highlight the content of the 4th cell - the content is selected, and the cell is current.
About selecting (making current)
The selecting in a table, except in case you want to format something or paste something, is generally a matter of placing the insertion point in a cell.
On the following screenshot, we clicked in the second cell of the second row. At that point, GN4 considers as selected all of listed below:
•Second cell of the second row
•Second column
•Second row
The real distinction is in the operation you do next.
If you choose to edit cell, you will edit the second cell of the second row.
If you choose to edit column, you will edit/format the entire second column.
If you choose to edit row, you will edit/format the entire second row.
About highlighting
If you need to paste content from Excel or any other software, then you need to perform the real selection, either by dragging by mouse or using the commands to select.
See also
Select cells and highlight content