libgdx

I'm just going through the javadoc and various tutorials on libgdx and I'm at the stage of trying to figure out differences between various concepts that seem similar to me or provide similar capabilities in libgdx. At first I thought scene2d was about creating interactive items such as menus, etc but various tutorials I'm reading use scene2d/actors for the main game items (i.e. the player, etc) and others just use sprites. What exactly is the difference between using Sprite and Actor (i.e. scene2D) in a game and when should you choose? Thanks. A Sprite is basically an image with a position,

I want to make a top-down 2d shooting game using libgdx. There will be a lot of bullet objects that I want to keep track of and dispose when they go off the screen. I was thinking that I would use something like static ArrayList<Bullet> bullets; to keep track of my bullets in the Bullet class, check this array list for any bullets that are off the screen, dispose of them if they are, and delete that bullet from the ArrayList. I was wondering if this is the best way to do this. It seems like something that should be pretty common and so I wanted to make sure that this is the best way of doing