Wikipedia
Phytosome is a complex of a natural active ingredient and a phospholipid.
It is claimed that phytosome increases absorption of "conventional herbal extracts" or isolated active principles both topically as well as orally.
The complexation with phospholipid has been applied to many popular herbal extract or active molecules including Ginkgo biloba extract, bilobalide isolated from Ginkgo biloba, silybin isolated from milk thistle ( Silybum marianum), curcumin isolated from turmeric, and green tea extract ( Camellia sinensis).
An attempt to trademark the term in the USA failed on appeal. Legal analysis in the USA held "...Applicant's fatal error, according to the Board, was in using the term as the sole designation for its new product." At least one dictionary has defined it as "a new term cosmetologists are using for the combination of liposomes ... and plant extracts."
Nevertheless, Phytosome is a registered trademark of Indena S.p.A., Milan Italy in most of the world (Australia, Canada, India, UK...)