There are three main kinds of crowdfunding: Reward Crowdfunding (think Kickstarter), Equity Crowdfunding, and Debt Crowdfunding. They each have their advantages and disadvantages. As others here have mentioned, reward crowdfunding can be difficult if you don't have a physical product. It certainly has advantages, including a potential boost in marketing/PR, but it simply won't work for most service businesses.
Equity and debt crowdfunding aren't too different from traditional equity and debt financing, with the difference here that you're raising money via an online platform. With equity crowdfunding, you're giving up a stake in your company for a significant cash boost, and with debt crowdfunding, you're taking on debt for the same thing.