Most regular movies are at leas 90 minutes long. 'Short movies' are... shorter. Episodes of tv-series are often about 20 minutes long, but some series actually make them about 40 minutes - which on tv often leads to almost a full hour of that show, because of commercials. I don't know what the term of things would be, between 50 and 60. I think at 60 minutes the short movies start, but that's just a guess.
Oh right. Wikipedia:
''A short film is any film not long enough to be considered a feature film. No consensus exists as to where that boundary is drawn: the Academy of Motion Picture Arts and Sciences defines a short film as "an original motion picture that has a running time of 40 minutes or less, including all credits".[1] The Internet Movie Database draws the line at 45 minutes.''
So... Episodes can also be short movies?