Company-specific: quarterly results, a big order win, a management change, an investigation, a product launch. These matter most for the actual long-term price.
Sector-specific: an oil price spike helps energy stocks and hurts airlines. RBI raising interest rates pressures banks' loan books but improves their NIM. A sector rally lifts most stocks in it.
Market-wide: budget announcements, RBI rate decisions, FII (foreign) flows, US Fed actions, geopolitics. These push whole indices up or down.
Noise: some days there is no reason. Prices move because a few big traders needed liquidity, or because an algorithm triggered. Not every move deserves an explanation.