A flash drive is a small portable storage device that uses flash memory to store and transfer data. It is often used to store and transfer files between computers, as it is small, lightweight, and easily portable. Unlike a hard drive, which is a larger and more permanent storage device found within a computer, a flash drive can be easily plugged into a USB port and accessed on multiple devices. A modem, on the other hand, is a device that connects a computer to the internet.