From LightWiki

Simply put, an item's Heading is the direction it is facing. In LightWave precision is required so a heading (or Pitch, or Bank) is given in degrees (accurate to two decimal places) around a 360° circle around the Y-axis, which in LightWave points straight up and down. 0° and 360° are both pointing towards North. Heading is represented in LightWave by a red circle surrounding the item.