A "crowd" of people who agree with a particular person trying to achieve some project provide money to fund it. The person pursues their project using the collected funding and shares some return (products, memorabilia, money, sense of accomplishment, etc.) with the funders if the project is completed successfully.
Crowdfunding is currently used widely to support art, development of inventions and free software, personal and corporate projects, disaster relief, political movements, venture funding, and more.
BitFlyer operates a crowdfunding platform using Bitcoin called "fundFlyer" (http://fundflyer.bitflyer.jp/). We are currently looking for projects. Please apply if you are interested.