The weather stripping show below is known as a “ribbed strip.” This weather stripping goes on the sides in the channels, at the head and on the sill. A groove is cut in the sash to slide on the track and lock in place when closed.
Below is a weather stripping called a J-Hook. This weather stripping is installed where the upper and lower sash meet. Known as the Meeting Rails where the Sash lock is located. Depicted below is how the j-hooks come together when the windows close creating an air tight seal that will last generations of use.