what is the mean of function ?I want to know something about function in c++,and how to use it in programming !especially in function overload!help!

A class may have several constructors, for example:
class myClass {
//constructor 1
myClass(int nx,int ny, int size){ c = nx * ny;};
//constructor 2
myClass(int nx,int ny, int nz, int size){ c = nx * ny * nz;};
.
}
When you generate instances of myClass, you may use:
myClass d2,d3;
d2.myClass(nx,ny,c);
d3.myClass(nx,ny,nz,c);
or use
d2.myClass(nx,ny,c);
.
b = a / c;
d2.myClass(nx,ny,nz,c);
.
b = a / c;
the later 2 d2.myClass() are "function overload",
one with 3 parameters and another with 4 parameters