How does compatibility work?

[Spira]

I have looked in the notes and found the following:

Compatibility - Compatibility with other species for breeding purposes. A comma-separated list of two numbers. If either number is 15, this species can't breed. In general, these numbers should be the same for each species in the same line of evolution. However, for baby Pokemon that previously weren't the lowest evolutionary form (e.g. Azurill, Pichu, Wynaut) these two numbers should each equal 15.

Meaning of each number: 1="Monster"; 2="Water1" (sea creatures); 3="Bug"; 4="Flying", 5="Ground", 6="Fairy", 7="Plant", 8="Humanshape", 9="Water3" (shellfish), 10="Mineral", 11="Indeterminate" (ghosts, having no defined shape), 12="Water2" (fish), 13="Ditto", 14="Dragon"

However it really explains nothing other than 15 being unbreedable. So what do these two numbers mean exactly? I am assuming that if atleast one matches another Pokemon they can breed. OR... do all of them have to match eachother? Just the first number has to match, do both? Are both numbers meaning male/female? Really the documentation sucks on this. Any information would be appreciated.

 

[Maruno]

This is really a question of how Pokémon works, rather than how Essentials works. Bulbapedia has a page about it (the "compatibilities" are actually called "Egg groups").

The Essentials wiki describes how Essentials works, not how Pokémon works. If you're using Essentials, it's assumed you know what a Pokémon game is. The documentation "sucks" because it's not supposed to exist there.