When I tell "real" I mean that you really want to hit your opponent with your weapon (for example, one from Ultrasabers) while he actively opposes you and tries to hit you as well. In this circumstances that "Forms" are absolute nonsence. if you'll try to use any of them against me in the tourrnament I would be absolutely happy because it will give me the easiest victory I can hope for.
Well, yeah...
...if you're doing stage fighting moves using the performance art styles of fighting shown in the movies and games.
But people don't do that. The "real" (as in real-world combat style) lightsaber forms take the lore and the philosophy/theme of each style and build a set of techniques, derived from real-world martial arts, based on those ideals. They are designed with functionality in mind and someone who trains in such methods can be realistically expected to fight well if they learn the form well, much like any other real-world style.
As for the original question though, there are two very distinct answers because of the dividing line I referenced above. Canon/lore-based lightsaber forms, and real-world practical renditions of lightsaber forms are by necessity quite distinct from one another. I don't know a lot about the specifics of the real versions of the forms, but I do know a fair bit about real-world fighting in general, as well as the lore behind Star Wars and its lightsaber forms. With that in mind, I'll add my voice to the comments about canon/lore related stuff primarily, with references to how they are adapted to the real world rather than a focus on the real-world adaptations themselves.
Form 1 is a singular and very specific "beginner" style, and the starting point for any aspiring Jedi or Sith in most eras of Star Wars where there are lightsabers and where there is any lore about their use. It's the most easily codified into a real-world fighting system because it's the only style with more than just aesthetic or philosophical basis on which to be defined. The next 4 forms (2 to 5) are distinct in lore, but less clearly-definable in terms of real world combat techniques. Most lightsaber users typically learn a little of each, but focus their efforts on a particular style from 1 to 5 which suits their body and/or their preferred method of resolving conflict. A special note needs to be made about form 5, since it has 2 sub-forms within it, both of which are form 5, but each of which is distinct from the other and will often be relied on by specific users to the exclusion or near-exclusion of the other. The sub-forms of form 5 have the same core philosophy to a point, but have enough differences to be easily argued to be separate forms. Form 6 in Star Wars lore is less of its own independent style and more of an informal title for the way a lightsaber user will fight if they refuse to focus on any particular "base" form and instead seamlessly blend elements of all the forms with little to no bias toward any given form of a lower number. The lore behind form 7 defines it as being almost entirely focused on aggression and unpredictability (even to Force users who can see the future and read minds) rather than actual "form" in a lot of ways. As such, forms 6 and 7 are the hardest to properly codify into any specific techniques, since form 6 is the use of aspects from all prior forms equally and form 7's defining attributes aren't actually things which translate to a codified fighting style.
Given that form 6 is often referred to as the "moderation" form, or the "diplomat's" form, it's got strong associations with the light side, but there are known wielders of the form among dark siders as well. Similarly, form 7 is explicitly stated to be fueled by emotion, which Jedi are trained to suppress, and is directly referenced as a primarily dark side lightsaber form, with very few practitioners in the light side. This leads me, personally. to consider it fair to treat forms 6 and 7 both as "mastery" forms incorporating the central philosophy of the opposing aspects of the Force into lightsaber combat using the relevant elements of all the prior forms. This is a personal perspective based less strictly on the lore and it can be very easily argued that canon contradicts my view in some ways.
