Sprite question

I thought that sprites did not have frames then how come when I do this, I can use the goto property?

in my main class I do this:

public var miniSprite:Sprite;

then in the main function:

miniSprite = new mcStuff();
playerClip.addChild(miniSprite);

mcStuff is a class that has linkage to a movieclip with multiple frames, so in a sense the sprite is holding a movieclip (the mcStuff class extends to MovieClip) is that right?