Final answer:
The Backspace key deletes characters while the left-arrow key moves the insertion point without deleting any characters.
Step-by-step explanation:
When you press the Backspace key four times, it deletes the four characters immediately before the insertion point in the text. This means that if the insertion point is in the middle of a word, pressing Backspace four times will delete four consecutive characters. On the other hand, when you press the left-arrow key four times, it moves the insertion point four spaces to the left, without deleting any characters.
For example, let's say the line of text is 'Hello World' and the insertion point is between the 'o' and 'W'. Pressing Backspace four times will delete 'orld', leaving 'Hello W', while pressing the left-arrow key four times will move the insertion point to the space between 'H' and 'e'.