What exactly is a "temperature" in the entropy equation

I know the entropy equation is change in thermal energy divided by the temperature equals change in entropy.

But what is temperature? Is it just a measure of it's temperature on a thermometer?

In another words what is a temperature?

Temperature and pressure (gas) are 2 ways of measuring the same thing(s) the average momentum or kinetic energy of the molecules in a system. The higher the temperature or pressure the more energy the system contains and thus the more useful work the system can do. 0th Law of Thermodynamics: Energy flows from high potential (high temperature or pressure) to lower potential (lower temperature or pressure) since energy flows from low entropy to high entropy this means high temperature or high pressure means low entropy

This all goes back to your Arrow of Time questions

At the Big Bang: High temperature, high pressure, high energy, Entropy = 0

The universe has been expanding (adiabatic), cooling, decreasing pressure, and increasing entropy ever since.

Universe has cooled to 2.725 degrees K

http://en.wikipedia.org/wiki/Cosmic_micr…

Sorry, I left out an important word. The sentence should read: The higher the temprature or pressure the more CONCENTRATED energy the system contains..........

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It is what should correctly be called the 'thermodynamic temperature'. It is sometimes referred to as the absolute or Kelvin or ideal gas temperature. It is measured in kelvin (K) and is proportional to the average kinetic energy of the the particles in te system.

It equals the temperature which would be recorded by a thermometer using an ideal gas as the thermometric medium. Other types of thermometer (e.g. based on mercury expansion) give similar temperatures but are not exactly the same except at chosen calibration temperatures.