What does attributeName specify?

Question

SoloLearn told that it Specifies which attribute will be affected by the animation

Answer 1

attributeName="x" make shape move horizontal while attributeName="y" make the shape move vertical

Answer 2

Its used in <animate> family tag and say to browser which property must animate (supposing thats animable)... Note that this is used n conjuntion with attributeType that specify if animable attribute is an xml attribute ('XML' value) or a css attribute ('CSS' value)