A family of Microsoft word processing software products for creating web, email, and print documents.
Since you clearly have nonprinting characters displayed, the invisible space is not an ordinary nonbreaking space, but a nonbreaking space will keep words together at a line break, so it would suit your purpose. Word's Symbol dialog offers two no-width breaks, but this is clearly not one of those.
You might explore the Symbol dialog for other sorts of spaces, but I'm not sure what point there would be to that if all you want is a nonbreaking space. If you're just curious about what the character is, select it and press Alt+X. That will give you the Unicode number of the character.