Differences between the keyboard right and left Shift key
The left and right Shift key on a computer keyboard perform the same function. When pressed and held down, it changes the case of the letter to uppercase, or use the alternate character on any other key. For example, pressing and holding down the Shift key while pressing the letter "a" makes a capital "A".
The reason there are two Shift keys on a computer keyboard is to make it easier to use the Shift function with all keyboard keys. For example, it's easier to use the left Shift key with all the keys on the right side of the keyboard. Similarly, the right Shift key is best used with all keys on the left side of the keyboard. Try using the left Shift key to make a capital "A" without re-positioning your hand. As you can tell, it's easier to use the right Shift key to make a capital "A" than the left Shift.
Finally, when a keyboard shortcut key requires the Shift key, the left or right Shift key can be used. For example, the Shift+Home shortcut key to highlight all text to the home position of a line can use the left or right Shift key.