They are called solids, liquids and gases respectively.

Microscopically, this is the difference in molecular spacing of objects.

The molecular spacing of gases is very large, and most of them are in a free state.

The molecular spacing of solids is small, and chemical bonds or molecular bonds are formed between them, which makes solids have a fixed shape.

The molecular spacing of liquid is similar to that of solid, but the binding form between molecules is different from that of solid.

In addition, there are actually many forms of gathering:

The neutron star is supersolid, and the peripheral electrons of all atoms are tightly pressed around the nucleus. The molecules are closely arranged, because there is no molecular vibration, so there is no temperature. The temperature of matter in supersolid is absolute zero.

There is also plasma state; Some state between solid and liquid, such as the state in which the glass body melts between crystals.