What does being lukewarm mean in contrast with being hot or cold for the church of Laodicea? From Rev. 3:14-22(ESV)


  14 “And to the angel of the church in Laodicea write: ‘The words of
  the Amen, the faithful and true witness, the beginning of God's
  creation.
  
  15 “‘I know your works: you are neither cold nor hot. Would that you
  were either cold or hot! 16 So, because you are lukewarm, and neither
  hot nor cold, I will spit you out of my mouth. 17 For you say, I am
  rich, I have prospered, and I need nothing, not realizing that you are
  wretched, pitiable, poor, blind, and naked. 18 I counsel you to buy
  from me gold refined by fire, so that you may be rich, and white
  garments so that you may clothe yourself and the shame of your
  nakedness may not be seen, and salve to anoint your eyes, so that you
  may see. 19 Those whom I love, I reprove and discipline, so be zealous
  and repent. 20 Behold, I stand at the door and knock. If anyone hears
  my voice and opens the door, I will come in to him and eat with him,
  and he with me. 21 The one who conquers, I will grant him to sit with
  me on my throne, as I also conquered and sat down with my Father on
  his throne. 22 He who has an ear, let him hear what the Spirit says to
  the churches.’”


Basically, Jesus Christ wanted the church to be either hot or cold, but never lukewarm. So my question is what does hot, cold, and lukewarm represent for this verse?
In addition to what was said before hot and cold being opposites one a passionate for God and another being cool. Both hot and warm water were considered luxuries during the days in which the epistles were written and both had positive qualities. Stagnant lukewarm water however had a special meaning to the Laodicean's as is related in the following explanation from March 5 2013 Sparking Gem From the Greek by Rick Renner:

The city of Laodicea was built in a region that was full of seismic activity and had experienced many earthquakes. As often happens in a seismic area, vents came up from the depths of the earth, allowing boiling hot water to reach the surface. In the nearby city of Hierapolis, these hot springs were famous. People came from great distances to bathe in those waters, believing they had medicinal powers. An experience in those waters was viewed to be therapeutic and effective in improving one's health.
Another city named Colosse was not too far away. As Hierapolis was known for its hot springs, Colosse was known for its cold waters. Just as people journeyed to Hierapolis to bathe in the hot springs for health purposes, people would travel great distances to vacation in Colosse, where they could invigorate themselves by taking frequent dips into the famous, refreshing, cool-to-freezing waters of that city.
Laodicea may have been the biggest and richest city in the area, but it had neither hot nor cold water. Therefore, the people of Laodicea had to leave their luxurious homes and travel to Colosse if they wanted to enjoy fresh, cool water. On the other hand, those who desired to soak in the hot springs had to travel six miles to Hierapolis.
Once in an attempt to bring the hot water from Hierapolis to Laodicea, a huge construction project was commenced. The goal of those who initiated the project was to build pipes that would channel the hot water six miles from Hierapolis to the city of Laodicea. The pipes effectively delivered the water - a real feat of construction at that time. Sadly, however, the water lost its heat along the way. By the time the water reached Laodicea, it was not only lukewarm, but it had developed a sickening, nauseating taste. The taste was so revolting that no one wanted to drink it!