The handle is a little tool that allow you to quickly edit the transform of your sprite. You can access them via shortkeys.
This is the one by default. You can move your sprite around the axis you want. For a full control, hold “Ctrl”. Then you can move it around freely.
By holding “S”, the scale handle will appear. You can then scale your sprite along the axises. Note that if the sprite doesn’t have an image,the first of its body will by also scaled. It’s very useful if you want to create triggers or invisible collisions.
By holding “R”, you make the rotate handle appear. Move it around the sprite to make it rotate.