Christine gave you a good explanation.
There’s kind of a continuum. Most “brand name” programs fall into the very structured and mostly structured categories.
Very structured: For example, some formats you exactly what moves to do, how many repetitions, and how to cue them. Whole class is prescribed and you must memorize and teach it their way. Les Mills, Turbokick, Red Warrior. The pros of formats like this are that a gym can hire several instructors to teach the same format and they will all teach it similarly, making subbing easy. And branded formats spend a lot of marketing $$$ so that clients know about them, which brings them into the gym. Also, some of the formats have assessments to ensure minimum quality standards, so it sets a sort of a bar of minimum quality to teach the format. That “pro” is also a “con” for instructors who want to be creative or members who get bored with the same thing.
Mostly structured: You have to use their routines and their music, but you can pick from a library of pre-choreographed materials. U-Jam is an example of this. You have to use their stuff, but they have about 120 routines to pick from. Pound is also like this – you pick the songs but you use their music / routines. I don’t teach RIPPED but I hear that it falls into this category because you have some choice of which segments to use. Same “pros” as the above.
Structured framework: You have a set of defined steps, but you get to mix them up how you want to. You can use your music or theirs. Bokwa is like this – 14 steps, but you can put those steps together in any order. Masala Bhangra, Fierce Funk, and Flirty Girl are also like this.
Loose framework: You have a general class plan and goals, but you get to pick movements and music to fulfill these goals. Bally Total Fitness used to have a class like this called Powerflex. The goal was a muscular strength and endurance class. We had a framework – warm-up, 4 minutes each of 8 muscle groups, cooldown, stretch. The exercises we chose for each segment were completely up to us.
True freestyle: The instructor sets the goal, designs the format, chooses the music, and determines the best way to teach it. The pros are the total creative freedom. As an instructor, to be able to set a goal for a type of class, design a program, teach it, and see results is HIGHLY satisfying. It’s what keeps me in fitness. The “cons” of teaching freestyle are that it’s hard to find someone to sub for you. Also, since there are no assessments or format rules, there can be freestyle programs that are truly great as well as freestyle programs that are truly awful. People keep coming to my classes but I’m not famous, so I think I’m somewhere in the middle. 😀
I am assuming you are asking about freestyle and pre-choreographed classes? (Both can be structured).
Freestyle classes are usually classes where the instructor has control over preparing the class–including any choreography and the exercises. It allows you to be creative while taking different skill levels into consideration.
Pre-choreographed classes are prepared classes where you follow a specific routine, format, and for a specified amount of time. Sometimes you must also use the music that comes with the program–and you also pay for the updates. (An example of a pre-choreographed program would be Les Mills–although I don’t necessarily know if it follows everything I’ve mentioned).
There are pros and cons to both, and you may find others answer this in a different way (this is how I’ve always understood the difference). Personally, I’ve always done freestyle and love preparing my own classes and having control. Hope this helps!