Thermal radiation and emission spectra

I have some questions regarding thermal radiation spectra of different objects. Is thermal radiation of objects due to electromagnetic radiation alone? Does my desk which is at room temperature emit as a blackbody with the proper factor for emissivity? Where is the "cavity" that the radiation is trapped inside for my desk? Is it the intermolecular spacing of the atoms in the desk? I have been thinking about this and getting confused or missing concepts. I think the theory has kind of clouded my understanding of the way that objects radiate, or just shown how little intuition I have of the way in which things thermally emit.

Also, this is probably a really dumb question but why is it that we consider a blackbody to a perfect absorber of electromagnetic radiation? Why should black be any different than for example red? It is technically a color in the "visible" spectrum

Thanks ahead of time for any help with my confusion