2nd moment of area, reference axis question
You are correct. The x-x axis is the major axis, and the y-y is the minor axis. In C3x6, 3 is the nominal depth (3"), and 6 is the weight per foot. If you draw a deflection diagram of a cantilevered beam with downward concentrated load at end, you will notice that the bottom flange carries compression, the web carries shear, and the top flange carries tension.
I am also new at this and maybe someone could tell me whether a C-section would be better or worse than an I-beam in a cantilever situation?