A USB flash drive, also known as a thumb drive or USB stick, is a small portable storage device that connects to a computer via a USB port. It is used for storing and transferring data between devices. USB flash drives are typically lightweight, durable, and have a high storage capacity. They are commonly used to back up and transfer files, such as documents, photos, videos, and music, from one computer to another. Additionally, they can be used to run portable applications or operating systems, making them a versatile tool for data storage and transportation.