After having a great idea, the goal for most founders is to get some money through the door. Ideally, every business would fund its growth and development through revenues (i.e. sales to customers) but unless you are able to produce a product or service overnight there is an inevitable delay between when you have the idea and when you are actually able to make your first sale.
With this, almost inevitable, delay, it is necessary to think about other sources of funding to grow your idea. Thankfully, there are typically lots of different opportunities for obtaining funding including friends, family, and fools (the founders themselves?), grants, accelerators, incubators, angel investment, venture capital, and private equity to name but a few.