Now's the chance to share your knowledge and experience in this area. Explaining the significance of a change in the stock market. As such, a single stock may rise when the market drops or drop when the market rises. Individual stocks rise or drop depending upon the number of sellers compared to the number of buyers - the old supply and demand theory. More buyers cause the price to rise.
More sellers cause the price to drop.
Generally, people decide to buy or sell based upon the past performance of the company or the anticipated future performance. Looking at the overall stock market, a rise represents the cumulative optimism that results in more buyers than sellers, while a drop represents the cumulative pessimism that results in more sellers than buyers. Many people look at a rise or drop in the stock market as an indication of good or bad economic times ahead. For long term investors, the daily fluctuations of the stock market should be no more than an interesting indication of how the market, in general, is doing. There are various measures for how the market is doing that investors can follow.