Shortcuts with arrow mostly are navigation shortcuts. They will help you quickly navigate to the location, or extend the selection.

What to doShortcuts
Open the dropdown menuAlt+↓
Move to the top edge of the data rangeCtrl+↑
Move to the bottom of current data rangeCtrl+↓
Move to left edge of current data rangeCtrl+←
Move to the right edge of the data rangeCtrl+→
Extend selection up to the first nonblank cellCtrl+Shift+↑
Extend selection down to the last nonblank cellCtrl+Shift+↓
Extend the selection left to the first nonblank cellCtrl+Shift+←
Extend selection right to the last nonblank cellCtrl+Shift+→
Move to the top nonblank cellEnd,↑
Move to the bottom nonblank cellEnd,↓
Move to the last left nonblank cellEnd,←
Move to the last right nonblank cellEnd,→
Extend selection by one cell upShift+↑
Extend selection by one cell downShift+↓
Extend selection by one cell leftShift+←
Extend selection by one cell rightShift+→
Move one cell up↑
Move one cell down↓
Move one cell left←
Move one cell right→