It means that, unlike embryonic stem cells, they are no longer totipotent. They can no longer differentiate into all the different cell types. Some of these cells are fully differentiated, while some are pluripotent, which means they still have the ability to differentiate into certain types of cells.
If we uncover the genetic "switches" which can turn a pluripotent stem cell into one of it's coded destinies, we may simultaneously uncover the genetics for turning fully differentiated adult cells into different cell lineages.