tcolorbox provides an environment for colored and framed text boxes with a heading
line. Optionally, such a box can be split in an upper and a lower part. The package
tcolorbox can be used for the setting of LaTeX examples where one part of the box
displays the source code and the other part shows the output. Another common use
case is the setting of theorems. The package supports saving and reuse of source code
and text parts.