Convert to Interlaced Video
When converting to interlaced video, each movie frame is turned into two or three video fields, which creates an uneven distribution. In addition, a movie frame may get split into odd and even video frames (note red asterisks above "*"). As a result, unwanted artifacts are created if there is a dramatic change of color, brightness or motion from one movie frame to another. See 120 Hz.
Movies to Progressive Video
When converting to progressive scan at 60 fps (60p), each movie frame is turned into four or six video frames, creating an uneven distribution. However, unlike conversion to interlaced video, there is no chance of odd/even splitting in the final frames. Converting 24p to 60p is essentially a 6:4 pulldown process.
Learn more about telecine