How do they affect the economy if they went up and high? what do they represent?
A stock market index is just a measure of the entire volume of a particular stock market. An example would be the Dow Jones Industrial Index, which is an index measuring the market for industrial stocks. Stocks are a way for publicly traded companies to attain capital for their operations, and stock markets are just markets in which investors can exchange their money in exchange for stocks which can either increase or decrease in value depending on the demand for their stocks (which is influenced by factors like the activities of the company, their future plans, market conditions, etc.). If an index goes up, it just means that there is more investment going on in the stock market, and vice versa. That is why people look at these indexes as indicators of what is going on in the overall market. However, just because an index is increasing doesn’t necessarily mean that an economy is doing better. There are all sorts of other factors, of which there isn’t a lot of agreement on, which affect the well-being of an economy.