Absolute zero is a theoretical temperature at which point all movement ceases. In objects that are at the temperature absolute zero, the particles aren’t moving; it has no kinetic energy and so zero temperature and zero thermal energy. Absolute zero is a theoretical temperature because scientists have never measured an object at this temperature.
If we had an object at absolute zero temperature and the particles started to move, the object would become warmer. The faster the particles move, the higher the kinetic energy, and thus the higher the temperature and higher the thermal energy. The hottest objects in the universe have extremely high kinetic energy, temperature, and thermal energy.
As stated above, when particles move around, they excite each other, thus releasing electromagnetic radiation. This means that all moving particles emit electromagnetic radiation, which means that all matter higher than the temperature of absolute zero emits electromagnetic radiation. Every object you can think of—the cardboard box, the table, you, the room, the house, the atmosphere, the world—are all releasing electromagnetic radiation as a result of their thermal energy.
Electromagnetic radiation released as a result of thermal energy is sometimes called thermal radiation. Thermal radiation can be any frequency, from radio to gamma. Keep in mind that thermal radiation is, like all radiation, just a stream of particles that can be different amplitudes and frequencies. The electromagnetic radiation itself, once released, is no different that electromagnetic radiation produced a different way; the electromagnetic radiation has no temperature. The term “thermal radiation” only refers to the way the particles got excited enough to release a photon.