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.
A text message is a short, typed message you send or receive on a mobile device. Text messages have a 160-character limit and can contain letters, numbers and special characters, like punctuation marks. They may also include links and emoticons.