Collapse is the end stage of pipe deterioration: cracks spread, roots wedge joints apart, ground loads crush weakened walls, and eventually the pipe caves in. Flow stops or squeezes through a fraction of the original bore, and soil washing into the void can sink the ground above.
A camera cannot pass a true collapse, so diagnosis rests on the visible entry point, sonde location and the symptoms. Repair almost always means excavation or pipe bursting — relining cannot bridge a lost bore.