VB.NET: what does the 'friend' modifier do?

friend in VB.Net is the same as internal in C#, it means that it can be accessed anywhere in the same assembly, but not from other assemblies.

I think it's a sensible default since I would say that normally one assembly should not be using another assembly's GUI controls (unless it's a class library or similar that is built for the purpose).

Friend is available in VB: The Friend (Visual Basic) keyword in the declaration statement specifies that the elements are accessible from within the same assembly,
From here

I believe the c# version is internal