Selecting table data is a preliminary step before searching it for text or exporting it. You can select table cells with mouse or keyboard.
Try selecting table cells with mouse, first with the CTRL key pressed, then with the SHIFT key pressed, and then with both keys pressed, to get an idea of how selecting with mouse works.
Then try pressing the navigation keys, such as the arrow keys, PAGE UP, PAGE DOWN, HOME and END, in combinations with the CTRL and SHIFT modifier keys, to get an idea of how selecting with keyboard works.
See also
Select all data in a view
Select a table row
Select a table column
Find text
Copy table data to Clipboard
Drag‑and‑drop table data to another application
Shortcuts for standard interface elements