VI snippets are like Screenshots of a Block Diagram, with one important difference. They can be opened in LabVIEW to reconstruct the orginal program. They are saved in the common
.PNG format so they can be used like normal pictures e.g. in forums and on StackOverflow.
To create a VI snippet mark the important part of your Block Diagram and hit "Edit → Create VI Snippet from Selection". Then choose where you want to save it. The VI Snippet has a border and a icon to indicate that you can drag them into LabVIEW to add the code to your Block Diagram.
This is what a simple VI snippet looks like: