The Wedge is merely a visual indicator for the Active Layer. Nothing is selected. The wedge is not an indicator of any artwork selection. It is no different than the highlight color when a layer is active. It's a remnant from when the app didn't have a color UI.
The Meatball directly indicates artwork selection.
- A double-ring Meatball indicates that object is selected.
- A filled Meatball indicates Appearance options are set for that object or layer.
- Double ring and filled Meatball means both of the above
- The little square is a visual map to where the selected object is located. The square will appear next to the selected object, then next to the meatball for any hierarchy necessary to navigate to that selected object. This allows you to see at a glance the containing Layers, sublayers, groups, etc that contain the selected object. The square appears when something is selected, but is not an indicator that something is selected on that layer. Only the Meatball indicates actual artwork selection.
The Meatball on a layer, sublayer, or group indicates everything encompassed on that layer is selected, hence the little squares. It's a bit of an inconsistent UI.. in reality, in addition to the little squares, all sub-objects should also have a double-ring meatball.. but Adobe has never been overly consistent in such matters.
It's important to realize that in Illustrator layer highlighting does not select any object. One can have a layer highlighted in the Layers Panel while altering objects on a different layer. AI's layer highlighting (and the wedge) are there for layer operations such as combining layers or moving layers around in the Layers Panel. the highlighting (and wedge) have nothing to do with actual artwork.