The email templates used by CONNECT, GUEST, and IDM are generated using Microsoft’s Razor markup syntax. Razor supports HTML, Razor markup, and the C# programming language and uses the @ symbol to transition from HTML to C# or Razor Markup. When the @ symbol is reached it will look to identify a Razor-specific markup, if it doesn’t then it will assume its C#.
Additional information on Razor Syntax can be found here..