A picture can be worth a thousands words. You can find many interesting and self-explanatory pictures here: http://spindynamics.org/Spinach-examples.php
In a nutshell: Spinach is not a program, but an open source library; it's something for programmers, not for end users. The language is, once again, Matlab. When the language is Matlab, usually that the programmer and the end user are the same person.
The purpose of Spinach is, once again, to simulate NMR experiments and spectra, of all kinds. With this latest arrival, I am even more convinced that the vast majority of NMR software belongs to the class of simulation software. The mole of published material (in the sense that you can find an article in literature) is inversely proportional to the number of users. It is a fascinating field nonetheless. You can freely download Spinach and read it. Installing it is a different story.
[NMR paper] Motional effects on NMR structural data. Comparison of spinach and Escherichia coli a
Motional effects on NMR structural data. Comparison of spinach and Escherichia coli acyl carrier proteins.
Related Articles Motional effects on NMR structural data. Comparison of spinach and Escherichia coli acyl carrier proteins.
Biochem Pharmacol. 1990 Jul 1;40(1):7-13
Authors: Kim Y, Ohlrogge JB, Prestegard JH
Proteins in solution need not exist in a single rigid structure but can exist in a dynamic equilibrium among structural forms. The problems that this poses for structure determination using nuclear Overhauser effect data from...