What is a semiconductor?

Semiconductor is a key industry for national development in the past two years. What exactly is semiconductor?

All objects in life can be roughly divided into three categories based on their conductivity: conductors, semiconductors, and insulators.

This is easy to understand. Objects either conduct electricity, do not conduct electricity, or have a little bit of electricity. It is precisely this half baked and unclear substance that gives physicists different opportunities to play.

Absolutely conductive and non-conductive substances are meaningless, while things with varying conductivity under different circumstances are interesting.