A window sliding vertically with two parts (sashes) that overlap slightly and slide up and down inside the frame.
A single hung sash window has one movable sash (usually the bottom one) and the other one is fixed.
A double hung window has two sashes, an upper sash and a lower sash, positioned one over the other to allow venting from the top or bottom.
A piece of sloping brick edge, clinkers or the like forming the base of a window. On the outside it covers the wall from the bottom frame till the edge of the wall. It leads away the water from the window and the façade. When on the outside, also called window ledge. The term sill or cill is used for both inside and outside.