Bred pokemon will inherit the parents IVs in 3 stats without a power item, these are chosen randomly. If it happens that a stat is chosen twice, the second time the IV is chosen the new IV will replace the first one ex- umbreon & espeon breed, the hp IV is chosen from umbreon & hp & Sp attack is chosen from espeon, espeons hp IVs will be given to the baby.
Hope this helps :)
EDIT- the other IVs for the baby will be chosen randomly, then there are also the power items that j98 has explained