Stock prices are driven by the demand and supply of the traders. The market is controlled by the cumulative actions of all the traders and cannot be manipulated easily, except by strong hands.
Fundamental analysis can be used for investment provided all the economic, financial, qualitative and quantitative factors of the company are known. This information is accessible only to strong hands. Therefore traders must stick to technical analysis, which only requires stock prices of a period as input.
Penny stocks are cheap and traded at smaller exchanges. They are not preferred because these companies do not make much profit and the traders are usually scammers.
The different types of graphs that can be used for studying are line graphs, bar graphs and candlestick graphs.