plain text

sometimes i can't send an email to my discussion group, and i ask to moderator then he answer that every email in html format always reject and he ask me to use plain text in order to send any message to my discussion group. what is the difference between it?

HTML stands for HyperText Markup Language. It's the way web pages such as this one are encoded to handle things like bold, italics and even color text. Plain text is, well, it's plain. There are reasons and times you might want to use both. Switching's not hard, if you know where to look. In the beginning (so to speak) there was plain text. Quite literally, plain text is text, and only text, along with a couple of simple representations for things like end-of-line. Plain text has no formatting. Plain text typically is represented as looking very plain. It's often displayed using what's called a "mono-spaced" font - meaning that each character takes up the same space on the line.