what is the stock?

When you buy stocks there is always a person who sells it and when you sell stocks there's always a person to buy it. The price you have to pay for bying stocks is the price another wants to sell for it. When you want to sell stocks of a company and there is little intrest for others to buy while there are more people who wants to sell,you have to sell it on a much lower price or you must change your mind and keep it. When you want to buy stocks of a company and there is a lot of intrest for others to buy while there are just little who wants to sell it the price should go sharply up to create more sellers and less buyers. an example : Yesterday the price of the stock ABC was 19.75$ ,now on opening there are 100 ABC who wants to buy on 20.2 $ or less 200 ABC who wants to buy on 20.05$ or less. There were only 150 ABC who wants to sell on 20.15$ or more and 250 ABC who want to sell it on 20.3$ or more. The openingprice ABC is 20.15 $ and there is a transaction of 100 stocks.(there are still 50 stocks to sell on 20.15$ but there isn't anyone to buy on these price,the 100 stocks whose order was earlier (of the 150 stocks) are sold). The next bidprice is 20.05$ and askprice is 20.15$. When you want to buy 50 ABC or less it's possible on 20.15$ and when you want to sell 200 ABC or less you can do it on 20.05$,when you want to buy 51-300 ABC the price should go up to 20.3$.