File "proj" contains information for the construction of the first-guess Wannier functions.
As the first-guess Wannier functions of a magnetic system may be different for majority and minority states, one may also set up files "proj.1" and "proj.2" instead of the "proj" file. In that case "proj.2" is used for minority Wannier functions while "proj.1" is used for majority Wannier functions. If the number of bands is different for minority and majority one needs additionally minSpinDown and maxSpinDown in inp.xml.
The syntax of proj depends on whether the calculation is collinear or noncollinear/SOC:
Since setting up the proj file by hand can be cumbersome for huge systems, the proj file can be generated automatically from the information given in the file projgen_inp.