when landing if you are on the gliding slope you can see 4 lights 2 bright and 2 red on the left side of the runway. why can i see those lights on some airports especially JFK?
There was a fairly thorough discussion of this on a previous thread you should look up. Briefly, there are a variety of landing light configuarations at various airports and on various runways at the same airport. They provide guidance to the pilot on how his/her altitude compares to the ideal approach altitude. On the system you asked about:
4 white lights means you are higher than you should be at that point on the approach.
3 white and one red means you are slightly too high.
2 whites and 2 reds mean you are on the ideal glideslope
1 white and 3 red means you are slightly to low
4 reds means you are significantly too low and may be in danger of impacting either an obstruction or the ground short of the runway.