I am currently writing a paper about Flex. I know what is meant when someone talks about a component. But I don't know how I can define 'component'. Is there some kind of official definition for that?
When someone says component, they are generally talking about a single grahpical entity. For example, the back button of your browser could be considered a component, as could the "message reply" box that I am using to reply to you right now. A component can contain other subcomponents. HTH
The above defintion is accurate, but for Flex we might also say "most anything (visual items) that extend or inherit from class UIComponent".