The difference between Tenshi and normal Volks dolls is that Tenshi are completely asexual. Tenshi means 'Angel' in Japanese, and all Tenshi types come with a pair of wings. Most Tenshi are very limited releases and usually only available at special events held at Tenshi no Sato in Kyoto. However some of them are not limited and can be bought by anyone who visits Tenshi no Sato.
SeiTenshi are a little smaller than YoTenshi (YoTenshi are the same size as YoSD).