BELOW IS A BRIEF LIST OF THE MORE COMMON TERMS THAT DEAL WITH STAIRCASE CONSTRUCTION. CLICK ON THE TERM FOR A PICTURE AND DESCRIPTION OF EACH.

Balusters

Sometimes called spindles, balusters are the smaller vertical pieces that stand under the hand railing and between the posts. They come in several varieties.
Wood balusters come in square top and pin top, and can be either paint grade or stain grade.
Iron balusters come in many different styles colors/finishes and thicknesses.

Goose Neck

A transition that converts the flow of a hand rail between vertical and horizontal. Usually seen going from the rake rail to the guard rail in over the post rail systems, as shown in the picture.

Hand rail

also called rail, hand railing is the portion of the staircase that your hand will run along and grip. More specific names for it include rake rail, which is the railing that runs at a diagonal angle over where the steps are, and guard rail, which runs horizontally across balconies and landings.

Molding

Used for decorative purposes and to transition between pieces of wood, molding comes in numerous types and styles. The two kinds most often used in staircases are cove mold, and panel mold. Cove molding runs under the tread and against the skirting and riser. Panel mold, also called rabbeted panel molding, runs along the edge of the skirting and transitions between the thickness of the skirting and the wall.

Over the Post Rail System

A rail system in which the handrail sits on top of the posts. These rail systems give a more flowing and elegant look and feel to the staircase.

Paint Grade

Materials described as being paint grade are intended to be painted. They are used for their shape and not for their appearance. examples of paint grade materials are poplar and MDF.
All of the wood portions in the picture are paint grade materials and are going to be painted to match the rest of the trim in the house.

Post to Post Rail System

A rail system in which the handrail runs in between the posts. There are two major styles that incorporate these style rail system. The first is a craftsman style using box newel posts as depicted in the picture. The other is a more traditional style where turned ball top posts are used that have a flat section near the top for the railing to attach to and a ball or other ornamental detail to top it off.

Posts

Also called newel posts, these are the large vertical standing components that the rail attaches to. They come in a number of different styles that are broken down into three categories. Box newels, which are not turned and are very square used for post to post rail systems. Ball top posts, which are turned but made for post to post rail systems. Newel posts that are turned and made for over the post rail systems. All can come in either stain grade or paint grade materials and very in heights and widths.

Riser

The vertical piece of wood between each tread. Not to be confused with the rise of the step which is a measurement taken from the top of one step to the top of the next step. Risers can be paint grade or stain grade and usually match what ever material the skirting is.

Skirting

Also referred to as skirt board. Skirting is used on the walls and gives the staircase a more grand and pronounced look. Skirting is not technically needed, but vastly improves the look of the staircase. Skirting can be stain grade or paint grade, and made in varying widths.

Stain Grade

Materials classified as stain grade are intended to be stained and not painted. They are materials that carry their own beauty that shouldn't be covered up with paint. Examples include Oak, Maple, Walnut, Cherry, or Mahogany as well as many others.

Treads

The horizontal portion of the step. Treads come in two types. The first, solid treads, are one solid piece of inch thick wood that stretches the full width of the staircase. The second type are end treads/ wall treads, sometimes called false treads, only cover the ends of the steps to leave the middle section open for carpet.

Turn out

Usually used at the bottom of the staircase, the turn out is used to flare out the railing to make it a little more open. It also pushes the post to the side of the staircase instead of being mounted to the front and in line with the rest of the railing.

Volute

Usually used at the bottom of the staircase, the volute is used to fare out the railing even more than a turn out. It creates a more elegant and inviting look that grabs the viewer's attention to the staircase.

Wainscot

A paneled wall covering that greatly adds to the impact of a room or staircase. Wainscoting can be either paint grade or stain grade and very in height and size of paneling depending on the desired look.