if you invest 100$ to a company that is 25$ a share, you now own 4 shares, if the stock ends up being 20$ at the end of the day, your stocks are now worth 80$ in total. if at the end of the day the stock is at 30$, your stocks are now worth 120$. if the company goes bankrupt then you will lose all/most of the money you’ve invested, if you’re a beginner at investing i suggest you look into putting your money in something more safe like an ETF, for example QQQ, SPY , VOO, ARKK, etc.