A stock's price?

The "intrinsic value" of a stock would probably be some measure of book value and a minimum level of discounted cash flows. The "extrinsic value" would comprise of a premium on it's net worth and future cash flows. Typically blue chip stocks trade at a higher price-to-book, where riskier firms trade at lower price-to-book. It should be noted, there is no "right" value of a stock. Each and every day the net worth of a stock is evaluated through trading, based on the perceptions of market participants.

As to how the stock price actually increases and declines based on material earnings news, it is the buying and selling of shares from huge players, either through active trading or computer trading. Buying drives up prices as it takes out offers and selling drives down prices by taking out bids. If at any time there is a discrepancy between what an automated system believes is the true value, it will buy or sell to take advantage of the (perceived) difference. As news emerges on the wire, human traders and automated traders continually reevalute a stock's value and execute trades based on their undervalued/overvalued analysis.

If you can double your money you might want to open a lemonade stand.

Lemonade stands do very well. I worked for one before I went to college as a summer job. Bucco Denaro.

Price is set at what the market will bare. Whether it be the stock market, the automotive market or the lemonade market.

If it is good lemonade and the weather is hot, people will pull out several dollars from their walletta for an "Ice Cold Lemonade!". Same idea behind stocks, automobiles etc. etc. . . Oversimplified? Probably not.

If you were the sole proprietor of GLUU. You would own the only share. If GLUU kept making year over year record profits, wouldn't GLUU (your one share) be worth more and more each year? The company has value. It generates revenue. That revenue increases year over year. . . You make more money (as the sole proprietor) each year. Now divide that company into millions of shares. Get it?

Shares represent partial ownership of the company.

The market, buyers/sellers are who interpret a company's performance. This can something cause an overreaction, but the market always adjusts.

Simply because they believe that in the future, their position will be worth more. They can sell it or hold on it - doesn't matter. If they don't believe in the hype, they may short sell into the spike. However, don't think that just because a share is worth more or less that it will be so. Buyers and sellers drive prices...sometimes this may be an overreaction, either to the upside or downside, but adjustments happen as the markets continually reevaluate information. To make it simple - the firm's performance/leaderships/etc. produce results/profits/etc. and the buyers/sellers move the share price to account for this information.

It's still a buyer and seller thing.

however, the company's success could drive seller out and lure buyer in.

It's both. The stock price represents the actual value of the company and what traders value the company at.