The full form of SD is actually Secure Digital. This is a type of memory card format that will be used for different gadgets. Some would use SD cards for cameras while there are also some who would use SD cards as extra storage for their gadgets. There are a lot of things that are being made into digital form right now that it is vital for people to have enough space.
When people do not have enough space, then they would need to delete some of the images that they already have. This can be a problem for people, but it does not have to be, especially if you would choose a memory card with higher memory.