The C4 bomb is a vital part of any round in CS:GO. In the Skybox 3D client, you have different options for how to showcase the bomb.
C4 Avatar - beaming C4 indicator, that indicates position and static of the C4. C4 Avatar can be enabled in Options/Misc or Sidebar/Visual Tools. It is possible to toggle lights and sound of C4 Avatar via Options/Misc. If C4 Avatar is disabled, in 3D view, it will be replaced with 2D icon.