Take one minute of video. Look at the file size. Now how many of these 1 minute files can you fit onto an 8GB card in your particular format and camera/device.
SMS stands for Short Message Service, which is the formal name for text messaging. It's a way to send short, text-only messages from one phone to another. These messages are usually sent over a cellular data network. That's not always true, though, as in the case of iMessage below.
The SMS message typically consists of a unique code that the organization sends to the user's cellphone. After the user receives the message on his cellphone, he may type the code into the organization's website or email the code back to the organization.