In layman language, an external drive, which gets sometimes referred to as solid-state drive or merely the hard disk(HDD), is the computer storage connected to your computer via an external cable from outside, unlike an internal drive is inside your computer. There are various types of external hard drives available, and some of them usually can draw power over the data cable in use. Other external hard drives require you to have an AC connected to the wall for the hard drive to draw its power. An external hard drive is usually portable devices that add extra storage space to your machine when plugged into your computer.