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.
Plain text, unformatted text. Text file, a type of computer file opened by most text software. Text message, a short electronic message designed for communication between mobile phone users. Nowadays, text messages can include media (such as photos, music and videos) and are also called media messages.