Why would people want to invest in stocks in the 1920's?

What does "buying on margin" mean?

Many people felt so confident before the stock market crash, because in the 1920's, many people felt that the stock market could make the a lot of money. In the 1920's, the stock market was not represented as something for 'irrational investing'. Most forgot the stock market had the ability to change incredibly fast and they went ahead and invested their life savings.