League of Legends (LoL) Question: what is a rune page what does it come with plz help explain

When buying a Rune Page you will receive another empty Rune Page you can fill up with Runes. There are 30 Runes to own to have at least one complete setup of Runes. If you purchase nine Greater Mark of Attack Damage fo instance you can use them for multiple Runes Pages at the same time.

If you buy a rune page, you receive an empty rune page which you can put runes in.
For example, you can purchase a Cooldown Reduction Glyph for a small amount of IP to put in your rune page and in game, you would have slightly more cooldown reduction.
~CanadianBacon