"Embryonic stem cells are stem cells derived* from the undifferentiated* inner mass cells of a human embryo*. They can develop into each of the more than 200 cell types of the adult body as long as they are specified to do so. Additionally, embryonic stem cells are capable of propagating* themselves indefinitely. This allows embryonic stem cells to be employed as useful tools for both research and regenerative medicine, because they can produce limitless numbers of themselves for continued research or clinical use." (reference 1)

Continue reading or see the following websites for more information:

• https://www.sciencedaily.com/terms/embryonic_stem_cell.htm
• http://stemcells.nih.gov/info/basics/pages/basics1.aspx

*derived- originally taken from
*undifferentiated- not formed or marked differently; the same
*embryo- any multicellular animal in a developmental stage preceding (before) birth or hatching
*Propagating- a synonym to reproducing