Snippets are a way to store canned responses for Emails or SMS. You can use them for things like handling objections or repetitive sentences or phrases for responses.
You can insert a Snippet into a template or an email by clicking the icon in the image shown below.
There are also some more advanced use cases as well for "Spintax" which helps you change copy up in email templates. Spintax is a way to rotate the content in the body of an email to help with deliverability.
Below is a video on the Uptics Spintax Feature. Here is also a detailed article on the Spintax Feature using Snippet Groups