Stock prices change every day as a result of market sentiments. By this we mean that share prices change because of supply and demand. If more people want   to buy a stock (demand) than sell it (supply), then the price moves up.

Conversely, if more people wanted to sell a stock than buy it, there would be greater supply than demand, and the price would fall.
Understanding supply and demand is easy. What is difficult to comprehend is what makes people like a particular stock and dislike another stock. This comes down to figuring out what news is positive for a company and what news is negative.

The important things to grasp about this subject are the following:
1. At the most fundamental level, supply and demand in the market determines stock price.
2. Theoretically, earnings are what affect investors’ valuation of a company, but there are other indicators that investors use to predict stock price. Remember, it is investors’ sentiments, attitudes and expectations that ultimately affect stock prices.
3. Sometimes, operators in low volume stocks are also responsible for awkward movement in particular stock
4. There are many theories that try to explain the way stock prices move the way they do. Unfortunately, there is no one theory that can explain everything.