Can someone tell me what this function does?

OpenGL OpenGL: Basic Coding
1

I want to know what this function does.

GLdouble thickness, GLuint side, GLuint edge, GLuint whole)
{
  static GLUtriangulatorObj *tobj = NULL;
  GLdouble vertex[3], dx, dy, len;
  int i;
  int count = dataSize / (int) (2 * sizeof(GLfloat));

  if (tobj == NULL) {
    tobj = gluNewTess(); 
    gluTessCallback(tobj, GLU_BEGIN, (void (__stdcall *)(void)) glBegin);
    gluTessCallback(tobj, GLU_VERTEX, (void (__stdcall *) (void)) glVertex2fv);  
    gluTessCallback(tobj, GLU_END, glEnd);
  }
  glNewList(side, GL_COMPILE);
  glShadeModel(GL_SMOOTH);
  gluBeginPolygon(tobj);
  for (i = 0; i < count; i++) {
    vertex[0] = data[i][0];
    vertex[1] = data[i][1];
    vertex[2] = 0;
    gluTessVertex(tobj, vertex, data[i]);
  }
  gluEndPolygon(tobj);
  glEndList();
  glNewList(edge, GL_COMPILE);
  glShadeModel(GL_FLAT); 
  glBegin(GL_QUAD_STRIP);
  for (i = 0; i <= count; i++) {
    glVertex3f(data[i % count][0], data[i % count][1], 0.0);
    glVertex3f(data[i % count][0], data[i % count][1], thickness);
    dx = data[(i + 1) % count][1] - data[i % count][1];
    dy = data[i % count][0] - data[(i + 1) % count][0];
    len = sqrt(dx * dx + dy * dy);
    glNormal3f(dx / len, dy / len, 0.0);
  }
  glEnd();
  glEndList();
  glNewList(whole, GL_COMPILE);
  glFrontFace(GL_CW);
  glCallList(edge);
  glNormal3f(0.0, 0.0, -1.0); 
  glCallList(side);
  glPushMatrix();
  glTranslatef(0.0, 0.0, thickness);
  glFrontFace(GL_CCW);
  glNormal3f(0.0, 0.0, 1.0); 
  glCallList(side);
  glPopMatrix();
  glEndList();
}