What is hold short line on the airport diagram?

Answer 1

This is the line where a pilot will be told to stop before access to teh runway. This allows ATC to know there is one "waiting to go" and there in allows them to make sure incoming planes are given priority to land. No pilot may move passed a hold short until told by ATC to do so

Answer 2

They are different because

ILS holdline, (it's a red box labeled "ILS") just before entering runway, is a sign that told pilots to hold there to prevent the loss of transmitting signals for those who landing, if the aircraft continue taxi to the holding point, the landing aircraft would not receive the glideslope info. because the aircraft blocks it.

A short Hold line is a hold short of the runway stopping point that is used by ATC to place an Aircraft in readiness to accessing the runway. This allows for such things as inbound on finals approach to come in and land knowing that no other aircraft is on the runway - Hold points can vary at each airport where in busy lines ups a number of hold points will be marked on the final access points to the runway so pilots can move to and stop there in readiness to be "called forward" for take off. It helps manage busy airports and ensures that no one pilot takes up on them self to jump the queue to get away head of any other pilot