The objects are converted to Symbols in flash, so that objects can be used effectivley.

Video Tutorial:

In a "movie clip" type symbol can include many animations inside it. If a symbol is of type "button" it can just be used for a link. In case of "graphic" type, images are converted to symbols, so that it can be used anytime.

The above video teaches you how to Convert objects .

• Drag an image to convert, on to the stage from the library.
• Press "F8" to get the "Convert to Symbol" window.
• Choose the symbol type to "movie clip", select the registration point.
• "Registration Point" it displays a "+" sign on the boundries or in the center of the movie clip.
• Drag another image on to the stage, set its type as "Graphic".
• So that graphic symbols are created just for the flexibility of use.
• Finally we include an image file as a symbol of type "button".
• Usually the button symbols are used with links.
• View the video and see how the image conversion is done.