That's a good question, and thank you for asking it. The simple answer is that all currencies build their value based on people's belief in the ideas and institutions behind the currency. Is it a good way to have a monetary system which benefits people and creates a better economy? Are the people involved, and the organization(s) responsible for managing the currency, ethical, transparent and trustworthy? The more people who answer yes to these questions about a particular currency, the more demand for it will increase and it will gain value. This is called the network effect: the more people believing in something and using something, the more valuable and useful it becomes.

Here's a 3 minute clip from a recent interview in which I talk about what gives money its value: https://youtu.be/HyIW8ToQYCg

Having said that, the Grantcoin Foundation has plans to make Grantcoin more useful as a currency, regardless of how many other people believe in it. For example, we're going to be starting our own e-commerce store, selling a variety of products made by socially/environmentally responsible companies, in which people will be able to pay with Grantcoin.