It's all about

What makes a stock price go up and down is all based on what people think about it.

They consider things like:
  • How strong are the company's financials?
  • What's the competition doing?
  • Do they have a good product?
  • Are the company leaders making wise decisions?
  • And so on...

The popular perception impacts the demand for the stock. The prices are set by supply and demand in the market as buyers and sellers place orders based on their current perceptions.