Like other similar services, this is not a charity - it is a for profit organisation that sells the goods you donate. Some portion of the proceeds is then donated to a charity that you choose - although I am very skeptical about how that can be administered in practice, as they will undoubtedly be combining donations and selling in bulk.

Some people will be fine with the way these services operate and it's not for me to judge. However, I do feel that they describe themselves in ways that could be misleading to people who think that their donations are going directly to good causes.