Each user may specify a quote on the preferences page (or while creating your account). Your quote is displayed underneath your user name in every post you create. The posts display quote dynamically, therefore if you update your quote, all of your old posts will show the new quote when they are viewed.
To include part or all of a previous message in a reply to that message, or the quoted text itself. Newsreaders mark quotes with a special character at the start of the row, usually "," "|" or ":".
To include part of a previous post when you follow up to it. Quoting is a good idea because it lets people know what you're talking about. Quoted material often is preceded by "" and looks like: This is an example of quoted material. Here is some more quoted material, to let people know what you are replying to. This would be where your new comments would begin.