ASP.NET MVC3: What is the packages.config for?

This file is managed by the NuGet infrastructure. It's used to track installed packages with their respective versions. If you installed the ASP.NET MVC 3 Tools Update it uses NuGet by default to track packages such as jQuery, EntityFramework, Modernizr. That's why you might be seeing this file when you create a new bare bone project.

To learn more about NuGet (and I highly recommend you do as it is one of the best things to be added to VS and C#/VB in years) look here:

NuGet Frequently Asked Questions

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