Why do companies sell their stock?

Companies sell stocks to raise money for the company.

When a company wants to raise money they can decide to sell ownership of their company. To do this they determine the total monetary value of the company as a whole. They then determine how many fractions they want to divide the company into (each of these fractions is one share of that companies stock). Then the find investors who would like to buy partial ownership of the company and sell them the parts of the company.

For Example:

Lets say Company X is worth $15 milllion and they want to divide ownership of the company into 1 million parts. They would create 1 million share of Company X stock and each share would be worth $15. They could then sell the shares to investors who would then own part of the company equal to 1/1,000,000 times the number of shares they own.