Located in the top right region of the keyboard, the Insert key is quite underused. When Insert is activated, anything you type will overwrite the original text. Annoying if turned on unknowingly, but useful in some situations, such as when you're batch replacing text. It'll save you the extra keystrokes to backspace/delete. Watch the screencast below to get what I mean. I probably use it most when I'm coding and just making minor changes. How to know if insert is turned on: your text cursor changes to a box or a horizontal line instead of a vertical line. Another interesting use of the Insert key is to copy and paste .
Notes and musings of a lightweight nerd