The Design Gallery uses a fake language called "Lorem ipsum" in design template previews. In publishing and graphic design, Lorem ipsum is a placeholder text commonly used to demonstrate the visual form of a document or a typeface without relying on meaningful content. Lorem ipsum may be used as a placeholder before final copy is available.

You can read more about Lorem ipsum:

http://en.wikipedia.org/wiki/Lorem_ipsum
http://www.lipsum.com

To see your own text on the design press the Preview button in the top left of a project while editing it.