The Standard and Smooth dances are Foxtrot, Waltz, Viennese Waltz, and Tango. Quickstep is an"International Style" dance only. The Latin and Rhythm dances are Rumba, Cha Cha, and Samba. Paso Doble and Jive are "International Latin" dances only. Bolero, Mambo, East Coast Swing and West Coast Swing are "American Rhythm" dances only.
The Standard/Smooth dances are quite different from each other. Foxtrot (Slow Foxtrot) has a very even, flat, smooth, continuous movement. The Waltz (Slow Waltz) has a swooping up and down movement. The Viennese Waltz has a flat, smooth, traveling, rotating movement. The Tango has a strong, flat, pulsing, staccato movement. Quickstep has a fast, even, smooth, continuous movement (like a fast Foxtrot, but different).
The Latin/Rhythm dances are different from each other primarily because of the beat of the music. All of the Latin/Rhythm dances employ a lower body action called "Latin" or "Cuban" Motion. The "lower body" refers to the part of the body starting from just below the ribcage and extending to the floor. The "upper body" is defined as from the ribcage and up and remains still. The stillness of the "upper body" exaggerates the Latin/Cuban Motion. The International Style Latin/Cuban motion is slightly different from the American Style Latin/Cuban motion.
The footwork for the Latin/Rhythm dances is the normal Latin/Cuban Motion footwork (ball, flat weight changes). As per usual there are as always exceptions. For example; West Coast Swing has two forward walking heel steps. The leg action for all of the International Style Latin dances is the same (always moving to a straight leg). The leg action for all of the American Style Rhythm dances is the same as well (there is always one straight leg and one bent leg).
The action of the Latin/Cuban Motion is based on the beat of the music. That is what makes each of the Latin/Rhythm dances feel different. A "hip switch" in Latin/Cuban Motion is a weight change from one foot to the next. Rumba has a "Slow, Quick, Quick" beat. A step taken on the "Slow" (two beats) of Rumba results in a relatively gradual and controlled "hip switch". A step taken on the "Quick" (one beat) results in a faster "hip switch". This difference in "hip switch" speed is what gives Rumba its unique feeling. The Cha Cha beat is 1, 2, 3, 4, &. The 1, 2 and 3 are each whole beats and the 4, and the &, are each ½ beats. The whole beats (1, 2, 3) are complete "hip switches" and the ½ beats (4, &) are partial "hip switches" because there is not enough time for a whole "hip switch" action. The Samba beat is 1, ah, 2. The 1 is a whole beat, the "ah" is a quarter beat and the 2 is three quarters of a beat. The Latin/Cuban Motion is executed accordingly. Samba also has a slight pendulum action by definition. The rhythm of the music directly affects the Latin/Cuban Motion action and feeling of each dance.
The Standard/Smooth dances are different from each other not only in the beat of the music but also in the actions of the bodies and the power of its movement. The Standard/Smooth dancer's body is defined differently than the Latin/Rhythm dancer's body. In Standard/Smooth dancing, the "lower body" refers to the part of the body starting from the hip sockets and extending to the floor. The "upper body" is defined as from the hip sockets and up. The "upper body" (as always) remains still. The still "upper body" of the Standard/Smooth dancer essentially rides along on top of the "lower body". As the "lower body" rises and falls, sways, turns, rotates, etc., the "upper body" responds accordingly. The Foxtrot, for example, has a very flat body movement while the Waltz has a cresting and dropping (rise and fall) body movement. The power of the movement of the body also has an effect on the feeling of the each dance. The Foxtrot has an even, smooth power throughout the dance while the Waltz has horizontal and vertical power in its movement. Tango has a very pulsing, staccato flat power movement.
All of the Latin/Rhythm dances essentially utilize the same "upper body". The "lower body", through Latin/Cuban motion, responds uniquely because of the different rhythm each dance has in its music. The Latin/Rhythm dances are defined by their particular type of Latin/Cuban motion.
The Standard/Smooth dances utilize different "upper body" and different "lower body" actions as well as different types of power. The combination of these three elements is what defines these dances.
It is important in Ballroom Dancing that the dancer understands the character of each dance and how it feels. The actions of the "upper body" and "lower body", the music (type and speed), and the power and direction of movement, all determine the look and feel of each dance.