What are "blackbodies"?

[DontPanic]

What is a blackbody?

I only have a description of a blackbody as "...an object that emits its own radiation when heated, but does not reflect incident radiation." but this doesn't create a clear picture of what that is? Are we talking about particular types of particles? Certain elements? Certain types of everyday matter?
Does anyone understand what I'm asking and can answer this?

[granpa]

http://web.mit.edu/16.unified/www/FALL/thermodynamics/notes/node134.html

http://www.transtutors.com/physics-homework-help/thermal-physics/black-body-radiation.aspx

[Naty1]

In physics, a black body is an idealized object that absorbs all electromagnetic radiation falling on it. Blackbodies absorb and incandescently re-emit radiation in a characteristic, continuous spectrum

http://en.wikipedia.org/wiki/Blackbody

[D H]

Adding to Naty1's quote, black bodies aren't real. They are instead idealizations. Real objects reflect some incoming radiation and have atoms that change the spectrum from the ideal black body spectrum.

So if there is no such thing as a real black body, what is the use? The answer is simple: Many objects do behave quite close to that of an ideal black body. Modify the equations with reflectivity or emissivity and you get an even closer approximation.