This egregiously ornate one is located at the Chateau de Chantilly.
A baluster—also called spindle or stair stick—is a moulded shaft, square or of lathe-turned form, cut from a rectangular or square plank, one of various forms of spindle in woodwork, made of stone or wood, and sometimes of metal or plastic. standing on a unifying footing, and supporting the coping of a parapet or the handrail of a staircase.Etymology: French balustre, from Italian balaustro (“pillar”), from balausta (“wild pomegranate flower”), so named because of resemblance to the swelling form of the half-open flower.
Multiplied in this way, they form a balustrade. Individually, a baluster shaft may describe the turned form taken by a brass or silver candlestick, an upright furniture support, or the stem of a brass chandelier, etc.
The word banister (also bannister) refers to the balusters of a stairway. It has been defined as either a handrail, especially on a staircase, or such a handrail together with its supporting structures.
Photo credit Geoff Howell (detailsdiary on Instagram), via.