Understanding of CSS pseudo classes and understanding of CSS pseudo classes

Understanding of CSS pseudo classes and understanding of CSS pseudo classes

Because I have never been familiar with css pseudo classes much before, and I can't understand a piece of css code on the Internet.

A: hover span. title {color: red ;.........}

Currently, by querying the css manual, the css pseudo class only represents a State. a: hover only represents the tag in the suspended state of the mouse, which is no different from the general a tag usage, a: hover span. title indicates the span style of the label in the floating state of the mouse, and a span. there is no difference in title usage