Are Elderberries and poke sallat berries the same thing?
No, not by a long shot. Elderberry (Sambucus canadensis,) is a woody shrub. All parts of the plant except for the ripe berries are toxic. The ripe berries make excellent jelly and wine, and have antiviral properties. Very good for colds and flu and such. You can rub the leaves on you for an insect repellant. The pithy stems make good blowguns.
Poke sallet/pokeweed (Phytolacca americana,) is a herbaceous perennial plant. All parts of the plant are very toxic to humans, except that the young shoots can be eaten after being boiled in two-three changes of water. They still don't taste good, IMO. Pokeweed is so toxic that contact with your skin can cause mutation of your DNA. The roots contain cardiac glycosides.