Opens the Export Themes Dialog from which you can select options for exporting the selected Themes. This option is useful for packaging themes for mailing to other people or storing as backup.
Since Textures are not stored with theme packs (textures are stored in texture packs), theme packs are generally very small. However this means if you do not have the texture pack that a theme refers to, the theme's textures will not appear and it will be flagged as being Broken.