what is it that makes a magnet different from a piece of iron that is not magnetic

A magnet and an ordinary piece of iron are made of the same kind of atoms , but inside they are organized very differently.

Short answer

What makes a magnet different is that its tiny internal “magnetic domains” are lined up in the same direction , so their effects add up, while in an ordinary piece of iron those domains point in many directions and cancel out.

Inside the iron: tiny magnets

• Iron atoms behave like tiny bar magnets because of spinning electrons inside them.

• In iron, groups of these atoms cluster into regions called magnetic domains ; inside each domain, the atomic magnets all point the same way.

You can imagine each domain as a little crowd of people all facing one direction.

Non‑magnetic iron: domains jumbled

• In an ordinary, “non‑magnetic” piece of iron, the domains point in many different directions.

• Because some domains point one way and others the opposite way, their magnetic fields mostly cancel, so from the outside the iron doesn’t act like a magnet.

So the material can be magnetic, but its internal order is scrambled.

A magnet: domains aligned

• In a magnetized piece of iron, most of the domains are turned so that they point roughly the same way.

• When that happens, their tiny fields add together, giving one strong overall magnetic field with a clear north and south pole.

That large, organized field is what lets the magnet pick up paper clips or stick to your fridge.

How iron can become (or stop being) a magnet

• You can magnetize iron by putting it in a strong magnetic field (for example, near a powerful magnet) or stroking it many times in one direction with a magnet; this gradually turns more domains to line up.

• Heating a magnet or hitting/dropping it hard can shake the domains out of alignment, weakening or destroying its magnetism.

So the big difference isn’t what the material is, but how well‑aligned its internal magnetic domains are.