what is write protect in sd card

Its a small switch on the side of the SD card that prevent anything from being written or delete from it. Bascially its been put into a "Read Only" mode. Its like with the VHS, Casset's, and what not with that tab that was there to allow you to record to them and then if you remove the tab they can't be written anymore. But in this case its just a flip of a switch that is on the card is self to select on or off for write protect.