Temperature is a measurement of the average kinetic energy of the molecules in an object or a system. Kinetic energy is the energy that an object has because of its motion. The molecules in a substance have a range of kinetic energies because they don't all move at the same speed. As a subtance absorbs heat the particles move faster so the average kinetic energy and therefore the temperature increases.
The Kelvin temperature scale has a true zero with no negative temperatures. Zero Kelvin is called absolute zero. It's the lowest temperature theoretically obtainable, and is the temperature at which the particles in a perfect crystal would become motionless.
Solids, liquids and gases all have temperature. The particles within a solid aren't moving around, but they have vibrational motion. As the molecules of a solid vibrate faster their temperature increases. The melting point of a solid is the temperature at which the vibrational motion overcomes the forces of attraction holding the molecules in a solid formation.