inconsistent accessbility

Suppose you have this:

public class MyClass
{
    public void MyMethod(YourClass yc)
    {
         Console.WriteLine(yc.ToString());
    }
}

internal class YourClass
{
}

Note that both MyClass and MyMethod are public and so can be accessed from outside the current assembly.

However, YourClass is internal and so can't be accessed from outside the current assembly. This means that an outside caller would be unable to call MyMethod because (s)he wouldn't be able to access YourClass and is a simple example of inconsistent accessibility.

For a more complete discussion, check out this MSDN link:

http://msdn.microsoft.com/en-us/library/cx03xt0t.aspx