Plot snapshots are computer graphics files of type *.wmf. These are not needed for viewing or printing plots in Scientific Notebook. You will need these snapshot files if you want to use a Latex compiler to produce a dvi file of your document with another system, including with Scientific Word or Scientific WorkPlace. Also, you may want these files to paste into other documents.
You can also use these snapshot files as pictures in Scientific Notebook. To do this, first generate the snapshot and look on the Axes page of the Plot Properties dialog to see the name of the file. With a file manager, rename the file with an appropriate descriptive name. Then, in Scientific Notebook, use File + Import Picture to bring the picture into a document. This will no longer be an active plot, but will have the same appearance as one. The pictures of plots are sometimes preferable for on-line viewing as they do not take any time to generate. They can also be given to students as puzzles–although the plots themselves contain all the information needed to replicate them, the snapshot pictures contain no such information.