Web
ASP.NET—ASP.NET has evolved for 2015 and is now a unified, lean stack that allows developers to create all types of web applications. The latest version of ASP.NET is primarily focused on ASP.NET Model-View-Controller (MVC) and web application programming interface (API) applications. These solutions typically run inside a user’s browser but communicate with a web server for application processing. They use Hypertext Markup Language (HTML), Cascading Style Sheets (CSS), and JavaScript on the client but communicate across Hypertext Transfer Protocol (HTTP) to a server for centralized processing of code and data storage and retrieval. There are many project templates outside the defaults that are based on MVC. These enable various JavaScript-first solutions based on single-page application concepts (see the later bullet) as well as other web development types. The core, however, is a single ASP.NET stack to run it all.
Note
Microsoft deemphasizes the older style of web development based on web forms. Web forms are still in the current version of Visual Studio for backward compatibility. However, if you are building modern applications, you should consider MVC or one of the SPA templates. This gives you better separation of code, greater testability, and a simplified programming model based on open standards.
Web API—Nearly all devices speak HTTP. As a result, web services are the ubiquitous means for communicating from device to server. This is true for desktop, phone, tablet, and all manners of applications. ASP.NET speaks HTTP very well and has thus been extended to allow developers to create services similar to the way you create other ASP.NET MVC solutions. The ASP.NET web API is now unified with MVC for a single programming model.
Single page applications (SPAs)—Users are demanding richer client applications in the browser that often work like native applications running on an operating system. Developers have turned to JavaScript to make this work. Many JavaScript frameworks, such as jQuery, exist to make developing rich applications easier. Larger “frameworks” have created a whole new web client programming paradigm. Take AngularJS as an example. It allows developers to code using an MVC style on the client; the code runs in the user’s browser versus ASP.NET running on a server. These frameworks and application types are known as SPAs. A user hits a single page in his web browser, and that page works like an application behind the scenes serving up requests and updating the UI. This is in contrast to a website that moves from page to page with full browser refresh.