Russian-olives (Elaeagnus angustifolia) aren't a true olive -- their common name (and Latin name) comes from the way their fruit resembles olives. As far as I know the fruits are not edible by humans, but birds like them. Russian Olives are actually a nuisance plant in the west and for sure are considered invasive in the midwest and eastern N.America. They were introduced in the 1800s as ornamental trees, and have spread on their own, sometimes crowding out native species. They spread through waterways by their bouyant seeds -- the "olives."
I love the trees -- their gray green color compliments other landscape colors like the oranges, golds and reds of autumn in Montana. In the photo below, the Russian Olive is the foreground tree, pale green contrasting with the vivid warm colors of the other wetland trees here:
I wish I could use them in my landscape designs, but I try to avoid it because of their invasive nature here in Montana. In the meantime I can enjoy the "wild" Russian olives in places like this wildlife reserve, and I can design with the related native Buffaloberry, Shepherdia argentea, which has a similar color and texture, although it's a shrub not a tree.
There are other plants available for gardens and landscapes that have similar color -- that gorgeous warm gray green, almost silvery. Blue Fescue, Blue Oat Grass, Buffaloberry among the many.