I am a little confused about the difference between build and publish in the visual studio.
What is the difference between building a program and publishing a progr
Building and Publishing a project in VS are totally different things.
The build process involves compiling your project's code and storing the binary result into DLLs. You can find them under \bin\debug\ folder or \bin\release\ folder under your project's root. That depends if you're building in Debug or Release mode. These DLLs store the application's binary data and can be referenced into other projects.
The publishing process always comes after the build process. Let's suppose that you have a ASP.NET application. If you want to use your project, building your web application into DLLs will not be sufficient, since you need to host your web application into a web server which will be IIS or ASP.NET development server. It involves hosting your application to be accessed by client entities. Basically, you can publish web applications and web services.