Flash memory is so named because the data is written to and erased from using electrical charges. You may have perhaps heard someone say that they've  had to flash their mobile device. This is quite similar to erasing flash storage media on smartphones and smart devices, except devices with operating systems such as Android and iOS require a much more extensive procedure for flashing and reinstalling their operating systems. The end result, however, is very much the same in that the memory and storage areas are reset or wiped.

Flash storage chips come in two types, known as NAND and NOR flash memory, and are responsible for high-speed and high-capacity storage of data on flash storage media. They are newer types of EEPROM chips (an acronym for Electrically Erasable Programmable Read-Only Memory), and instead can wipe blocks of data or the entire drive, rather than just one byte at a time, as with the slower EEPROM. This type of flash memory chip is non-volatile, meaning that the data is still stored on the chip even after power to the chip is lost. Data is erased when specific instructions are sent to the chip in the form of electrical signals via a method known as in-circuit writing, which alters the data accordingly.

The following picture shows one of my old 1 GB flash drives with a Samsung NAND chip, which stores the data. If you'd like to get down into the technical details of the chip, you can have a look at the datasheet PDF at http://datasheet.iiic.cc/datasheets-1/samsung_semiconductor_division/K9K4G08U0M-PCB00.pdf:

Flash media storage has so far become the ultimate in portability, with many types ranging from the size of your thumb to the size of your nail on your little finger. The lifespan of flash storage all depends on the usage, as they all have an average read-write usage, sometimes displayed on the packaging of the device. The read-write speeds are also some of the fastest at this point, which is why hard disk drives have moved away from the traditional mechanical disk mechanism to a solid-state one. More on SSD will be discussed later in this chapter.