Insertion Loss vs Transmission Loss
They can be the same thing. A transmission line will attenuate an amount (based on distance) whilst maintaining impedances so, it could be regarded as causing "insertion loss".

Here's what wiki says about cable attenuation: -


  Insertion Loss
  
  Insertion loss, also referred to as attenuation, refers to the loss of
  signal strength at the far end of a line compared to the signal that
  was introduced into the line. This loss is due to the electrical
  impedance of the copper cable, the loss of energy through the cable
  insulation and the impedance caused by the connectors. Insertion loss
  is usually expressed in decibels dB with a minus sign. Insertion loss
  increases with distance and frequency. For every 3 dB of loss, the
  original signal will be half the original power (\$\sqrt2\$ of
  amplitude).


Taken from here