CSS issues

[ivanstepanovftw]

CSS page have really fuzzy explaination.

/* 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?

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/* 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?

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