Investopedia is a stock market simulator that allows users to track virtual portfolios and learn about investing. The author enjoys using Investopedia to understand how the stock market works with different stocks listed on the major exchanges like NASDAQ, NYSE, and AMEX. As a beginner investor, the author has experienced both profits and losses through practicing strategies on Investopedia. It is a good learning tool for understanding concepts like buying power, cash levels, and annual returns without the real risk of losing money in the live markets.