Temperature is the measure of hotness or coldness of matter. Stated another way, temperature is the average kinetic energy per molecule of a substance. Temperature is measured in degrees on the Celsius (C) or Fahrenheit (F) scale, or in kelvins (K). In simplest terms, temperature is how hot or cold an object is, while heat is the energy that flows from a hotter object to a cooler one. For example, the temperature of a cup of coffee may feel hot if you put your hand around it. It is hot because heat from the coffee is transferred to the cup.
Heat energy, or thermal energy is the energy of a substance or system in terms of the motion or vibrations of its molecules. The faster the molecules in a substance move, the more heat energy they have. You can transfer heat energy from one object to another, and in fact, a heat transfer will occur naturally whenever a hotter object is in contact with a colder one; heat will always move from the hotter object to the colder one. For example, if you were to put your warm hands against a cold metal pole, the skin on your hands would feel cold. That's because the heat from your hands transfers to the cooler metal. Your hands feel colder because some of your heat has been transferred to the metal.
When you add heat energy to a substance, one of two things can happen: either the temperature of the substance will increase, or the phase (or state) of the substance will change. Temperature is the average kinetic energy of the molecules in a substance. So it's pretty obvious why temperature might increase - heat is the motion of molecules, so if you get the molecules in a substance to move faster, then they'll have a higher temperature. But what about phase change?