I've been trying to figure it out, to no avail. In reading someone else's code, I come across a function definition, where it says something like this
UserDefinedFunction[a_Integer, b_Integer, c_Integer, d_, k_:Automatic]/;Abs[a]>b:=0;
I understand that it means the function should return 0 if Abs[a] > b, but what does the tag
k_:Automatic mean? What is it broader usage? How does it relate to when I plot something and tell Mathematica to assign
PlotRange -> Automatic?