SD cards are Secure Digital flash drives (like a USB thumb drive) but are typically smaller and work well with handheld devices. There are also micro SD cards that many smart phones (like Android Phones) use for additional memory. They're about 1/3 the size of a SD card.
i have a micro SD card in my phone so for me whenever i want to transfer pictures videos or add music i just pop it in the adapter and throw it in the SD slot on my 13" MBP.
SD cards are Secure Digital flash drives (like a USB thumb drive) but are much smaller and work well with handheld devices. There are also mini SD cards that many smart phones (like Android Phones) use for additional memory. They're about 1/3 the size of a SD card.