The "Page Down" key is a common feature found on computer keyboards. It allows users to scroll down a document or webpage quickly, moving the viewable area down by one screen length. This function is particularly useful for navigating long texts without having to use a mouse or touchpad. When pressed, the "Page Down" key typically shifts the content down, revealing the next section of the document. It is often used in conjunction with other keys, such as the "Page Up" key, which scrolls the content upward. This functionality enhances efficiency when reading or editing documents in applications like Microsoft Word or browsing the internet.