What IVs are, in plain terms
Think of IVs as the individual variation between two Pals of the same species and level. Two Anubis at the same level can have different stats because their individual values differ. The game does not present IVs as a single number you can edit, and community tools that report IVs are reading game data, not an in-game menu.
That means IV advice that promises an exact IV from a specific pair should be treated with suspicion. A pair decides species and passives. IVs are what you select for after hatching, by comparing offspring.
How breeders actually use IVs
The practical workflow is: breed the species you want, with the passives you want, several times. Compare the offspring's stats at the same level, keep the strongest, and breed from that keeper. Over generations, your keeper pool improves. Trying to optimise IVs before you have the species and passives is backwards, because a high-IV Pal of the wrong species or with the wrong passives is still the wrong Pal for the job.
For breed-true Pals, this is the main post-catch grind: catch one, breed same-species pairs, and keep the best offspring as the next parent.
What not to do
Do not spend Cake chasing a claimed IV recipe from a pre-1.0 guide. IVs are not a formula result, and a pre-1.0 species list will not give you the species you want in 1.0 anyway. Verify the species in the calculator, then select for stats among the offspring you actually hatch.
Frequently asked questions
Can breeding guarantee perfect IVs?
No. Breeding gives you offspring to select from. It does not guarantee a specific IV set on the next egg.
Should I care about IVs before passives?
No. Species first, passives second, IVs third. A Pal with the wrong species or passives is not fixed by good IVs.