A button can be anything that you can F8 Convert to Symbol. A button in Flash has four states: Up, Over, Down, and Hit -- ---- ---- --- It is traditional for the Over state to become a faded version or a larger version or an animated version of the button's Up state. It is typical for the Down state of a button to have the button shift position slightly, indicating it was just clicked. Usually the shift is downward and rightward. Of course, your button has an .addEventListener() method. Each instance of your button symbol will have an instance name. It is best practice to give the button instance name a suffix, as in myButtonName_btn, where _btn is the suffix indicating its a button.
The Square animation goes from Frame #3 to Frame #30. The squareSymbol is a Movie Clip symbol. The Circle animation goes from Frame #31 to Frame #60. The circleSymbol is type Movie Clip Symbol. The instance of the squareSymbol does NOT have an instance name. The instance of the circleSymbol does NOT have an instance name.