When I do a "Go To Definition" for a type in the c# code editor, say IDisposable, Visual Studio opens the Reference Source for IDispoable in the Browser: https://referencesource.microsoft.com/#mscorlib/system/idisposable.cs,1f55292c3174123d
How can I stop Visual Studio from opening a browser?
How can I tell VS to open IDisposable in the Object Browser?
Visual Studio does not do that by default.
I would guess that you installed an extension (like this one) that does it for you. Uninstall the extension and VS should revert to its default behavior.
Another possibility is that you enabled a feature in Resharper that does a similar thing.