The title says it all... but I'll elaborate:
- Initially we see techniques derived from a single chakra element (Katon, Doton, Suiton, Fuuton and Raiton). These are the most common, since usually a ninja can master only one chakra nature (since normally ninjas tend to have an affiliation with only one chakra nature)
- Later we discover these can be combined in a number of ways, creating new elements (Mokuton=Doton+Suiton, Ranton=Raiton+Suiton, Youton=Katon+Doton, among several others). From what I understand, these are usually transmitted as a Kekkei Genkai. But I believe they can also be created by the combinations of the elements, by ninja who didn't inherit it from other generations (correct me if I'm wrong). These are not uncommon, but less frequent than the ones above (there are ninja who can master and possess affiliation to more than one chakra nature: Sasuke comes to mind, since he can master both Katon and Raiton. Katon is his clan's natural affiliation, and he mastered Raiton too. However, I don't remember if he has ever combined the both of them)
- Even later, we find about combinations of even more elements by ninja who can master several elements, such as Muu (Nidaime Tsuchikage) and Oonoki (Sandaime Tsuchikage), who can combine Katon, Doton and Fuuton, to create Jinton. These are called Kekkei Touta. I don't know if they can also be transmitted through Kekkei Genkai, or if they can only be taught. They are even rarer than the ones above, since ninja can rarely master or be naturally affiliated to more than two chakra natures (Terumii Mei the Godaime Mizukage, can also master Doton, Katon and Suiton, but I don't think she ever combines more than two at each time).
My questions are:
- Are combinations of chakra natures taught or only transmitted by Kekkei Genkai (or both)?
- Are combinations of more than three chakra natures possible?
- And the above question created a new one for me: Can a ninja master more than three chakra natures? (I think Kakashi does, but I am not quite sure about this)