Snip used to write PHP code from Admin Panel. A Snip always execute inside a Static Page.
Location: Admin Panel > Page Manager > Manage Code Snips
After creating the snip we use it as a Page code in other pages. Each snip has a unique code that we place in content of static page. See below example
{{name=UI type=staticpage name=SnipName autoformat=off}}
See also Static Page