Running a business, whether your are a small, intricate business in your local neighborhood or a large corporate entity, is about as far from a "simple" task as you can get. There are myriad legal complexities to this immense responsibility, and a company, no matter its size, will need to be flexible and savvy when dealing with the many issues that can arise over the course of its existence.
First of all, a business has to actually get off the ground. In order to do that, the founder needs to establish what type of business it is (limited liability, a partnership, a corporation, etc.) and then put forth a business plan in order to keep the business on track (as well as to entice investors, if that is needed).
Second, a business will need employees. That sounds simple enough, but consider everything that comes with that. You need to draft contracts so that employees sign them and adhere to the rules. Then you then need to enforce those rules. You also have to abide by state laws for employee benefits, hours, and wages.
And then there are matters of legal importance relating to your business's interactions with other companies and your business's intellectual property. Trade secrets, patents, and trademarks are just the beginning. There are also the contracts that you agree to with other companies and vendors.
Adhering to the law while also promoting and running your business is essential to the entire process -- and sometimes that requires skilled legal counsel in the area of business and corporate law.