A semiconductor is a type of material that can conduct electricity, but not as well as a metal. It is formed by covalent bonds, which are strong bonds between atoms that involve the sharing of electrons.
In a semiconductor, the covalent bonds between the atoms are neither too strong nor too weak. This means that when energy is added to the material, some of the electrons can become "excited" and move around more freely. This makes the material conductive, but not as conductive as a metal where the electrons can move very freely.
Semiconductors are used in a variety of electronic devices, such as transistors and diodes, and are essential components in the modern electronics industry.