You can easily change the name and the description of your Moov. A description is not mandatory, but might be interesting if you publish a Moov to the Moovly Gallery, because its title and description are published as well.
To change the name and description of a Moov, click on its thumbnail to open the preview page:
Underneath the video player, you’ll see the current name (and description, if there is one) of your Moov. Click the 'Edit description' tab:
Clicking the 'Edit description' tab changes the view to 2 fields: one for the name and one for the description. Enter your text and click the Edit button.