MagSafe is a ring of magnets built into newer iPhones that lets accessories snap on perfectly aligned every time. Its most popular use is wireless charging — a MagSafe charger clicks onto the back and juices up faster and more reliably than a standard wireless pad, because the magnets keep the coils lined up.
Beyond charging, MagSafe powers a whole ecosystem: magnetic wallets, phone stands, car mounts and power banks that attach instantly. If you want to use any of these, pick a MagSafe-compatible case — it has the magnet ring built in so the connection stays strong through the case. Cases without it will feel weak or won't hold accessories at all.