A memory card is any small device that allows for a user to store files of a large variety on it for mobility. In other words, a user can take a memory card, insert it into a computer, put files on it–including text documents, pictures, audio files and video files–and then remove the card and bring it to another computer. Once at that computer, they can insert it into the computer and take the files off of the memory card and place them into a folder within the hard drive of the computer.
Typically, a memory card implements flash memory. Flash memory is memory that can be erased and written numerous times. It is because of this that people can delete files on their external memory card and then add new ones. The memory gets erased and it goes back to being a clean slate waiting for a new file to be added. More importantly, though, is the fact that it is a non-volatile memory which means that it is not prone to malfunction or data corruption.
When memory cards first came out, they were not very large and were incredibly expensive. However, as the years have gone on, it has become cheaper to develop and manufacture memory cards that hold more and are smaller in physical size. Therefore, it is not unreal for an average person to have a very large memory card that didn't cost much more than $50. This has made file storage much more secure for the average user.
There are numerous different types of memory cards. The largest in size and smallest in data capacity is the compact flash memory card. Then comes the SD memory card. Following that is the miniSD card and finally, there is the microSD card. As these cards have evolved, they have gotten smaller in actual size; however, they've grown larger in data capacity.
It is important to note, though, that a flash drive is not a memory card. While it does use flash memory and it does store things, it doesn't fall under the classification of a memory card. Instead, it falls under the classification of an external hard drive which is something entirely different.
