CSS issues

CSS page have really fuzzy explaination.

```css
/* You can select an element which is a child of another element */
div.some-parent > .class-name { }

/* or a descendant of another element. Children are the direct descendants of
their parent element, only one level down the tree. Descendants can be any
level down the tree. */
div.some-parent .class-name { }
```
It is unclear which element will be selected. `div.some-parent` or `.class-name` one?
What does "another element" mean?

---

```css
/* Warning: the same selector without a space has another meaning.
Can you guess what? */
div.some-parent.class-name { }
```
What should one guess in Learn X in Y? Why not just explain warning?

---

I didn't like this page and explaination of rules.