Snippets are named blocks of text that you can use in several topics. For example, when writing tutorials you need repetitive lines of text like "Select Main Menu -> File -> Open". But when your main menu structure changes and you rename menu "File" into something like "Project" you need to update all topics that describe actions associated with this menu. Instead of that you can create Snippets named "menufileopen" with the text "Select Main Menu -> File -> Open" and use it whenever you need to reference this menu. Now when your menu structure changes you only need to edit this snippet and recompile help file.
Snippets can also be parameterized, e.g. you can define block of text that will replace TEXTFORSNIPPET placeholder in the snippet text.
Here's sample snippet "Warning":
And here's how we will use it in our topic:
This is how it will look like when project compiled:
This is warning text.