What is the Meaning of the Icons in Edit Attribute Set Page

Question

In this screen snip we're looking at the Edit Attribute Set for the Default Attribute Set. What do these images/icons mean.

Answer 1

The icons with the "restricted" sign (red circle with a white line) are system attributes. They are created by magento and have special meaning. They cannot be removed.
You can do what ever you want with the rest of the attributes.