What is Flash drive?

A flash drive, related to a solid state drive, is a storage device that uses flash memory rather than conventional spinning platters to store data. Unlike a USB flash drive or keydrive, flash drives tend to physically imitate conventional hard drives in size, shape, and interface so that they may act as a replacement for hard drives.

A Flash drive in a standard drive form factor.
These products are typically used as low power, rugged replacements for hard drives, especially in installations exposed to extreme conditions. The flash memory cells tend to fail after around a million writes which made early devices unsuitable for storage which is often updated in place, such as swap files. To address this problem, some flash disk vendors have introduced wear-levelling techniques that track usage and transparently relocate the data in highly utilized extents of storage to extents that have been less utilized. Unlike solid state drives, flash drives do not generally require backup battery systems.
Another use for flash drives is running light weight operating systems designed specifically for turning general-purpose PCs into network appliances comparable to more expensive routers and firewalls. In this situation, a write protected flash drive containing the whole operating system is used to boot the system. A similar system could boot from CD, floppy disk or a traditional hard drive but flash memory is a good choice because of very low power consumption and failure rate.
As of 2001, limited quantities of consumer electronics (such as notebook PCs) have become available including flash drives in place of conventional hard drives[1]. It is widely assumed that this trend will increase over time as the cost of flash drives decreases and the performance needs of consumer electronics continue to increase.