To understand the great depression you first need to understand the Wall Street Crash. To understand to Wall Street Crash you must understand stocks and shares.

Shares are needed so that the capital to start and maintain a company can be raised. People buy shares in the hope of making a profit on their investment as all shareholders get a share of the company’s profits.

Shares are traded on stock markets like the LSE and AMEX

If a company is doing well then their share price will go up as more people want to buy the shares.
If a company is doing badly then their share prices will go down as less people want a share of that company.

I hope this has laid out the basics of stocks and shares, if you have any questions or comments, please leave them below and they will be answered.