The phrase "ionic form" refers to the state of an atom or molecule where it has gained or lost electrons, resulting in a positively or negatively charged particle called an ion. Full definition
For example, Premier Coral Legend Plus from Radiant Life (puportedly provides both calcium and magnesium in ionic form for better absorption) or Bone Renewal from The Synergy Company (similar claim but without magnesium)? (wellnessmama.com)