Razor is the dotnet templating language, Razor is the syntax used to create views in dotnet applications. It will normally be found in `.cshtml` files. You can think of it in a similar way to JSX, in that Razor is to C#, what JSX is to Javascript in a React application.

Templating languages don’t transform data, but arrange it for display in a view.

Example displaying a list in JSX:

const list = (items) => {
  return (
    <ul>
      {items.map((item, index) => (
        <li key={item}>{item}</li>
      ))}
    </ul>
  );
}

Displaying the same list in Razor

<ul>
@foreach(var item in items) {
  <li>@item</li>
}
</ul>

Further Reading

A great cheatsheet for copy + paste
https://haacked.com/archive/2011/01/06/razor-syntax-quick-reference.aspx/ 

A good abstract overview of templating engines as a whole:

https://thomaslevine.com/computing/templating-languages/

The Microsoft ASP.net Razor Guide

https://docs.microsoft.com/en-us/aspnet/web-pages/overview/getting-started/introducing-razor-syntax-c