what is a caper? I see this in alot of receipes, is it like an olive?!

Capers are actually immature buds plucked from a small bush native to the Middle East and Mediterranean regions of the world. Fresh caper blossoms are not especially flavorful, but their sharpness increases dramatically after sun-drying and brining in vinegar.

Capparis spinosa, the caper bush, is a perennial winter-deciduous species that bears rounded, fleshy leaves and big white to pinkish-white flowers. A caper is also the pickled bud of this plant. Caper bush is present in almost all the circum-Mediterranean countries and is included in the floristic composition of most of them but whether it is indigenous to this region is uncertain. Although the flora of the Mediterranean region has considerable endemism, the caper bush could have originated in the tropics, and later been naturalized to the Mediterranean basin.[1] The plant is best known for the edible bud and fruit (caper berry) which are usually consumed pickled. Other species of Capparis are also picked along with C. spinosa for their buds or fruits.

It is a pickled berry.