Businesses and companies contribute to economic development in several ways. First, they create more jobs for the public, which stimulates the economy (if I have a job, I have more money. More money allows a person to buy things (the money to buy things goes right back into our economy).Also, unemployment and welfare drop when companies and businesses are doing well enough to hire.
Businesses and companies ("Bus or Co") also pay taxes- the corporation pays its own taxes and so do its employees. This feeds money back into the government, thus allowing for a more robust economy.
Finally, when we have bus. and co.'s in existence, they have the capital and means to encourage innovation and new ideas. This is how inventions often come to fruition as well as overall improvement of the products and even the processes we already have. For example, it was through business entities that their hired employees collaborated to make car fuel systems more efficient, in addition, these innovators (fueled by funding provided by said co.'s) have created and improved countless things (like fire retardant carpet, safer windshields that ensure in a car crash you are not hit by shards of large potentially deadly pieces of glass from the shield).
These are a few of many things that Co.'s do to stimulate and further economic development.