private...function test lib "coredll.dll"...what does this do exactly?

[jcaulder]

Public Class MyNumericBox : Inherits NumericBox

Private Declare Function ShowIM Lib "coredll.dll" (ByVal dwFlag As Integer) As Boolean

Private Sub Me_GotFocus(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.GotFocus
ShowIM(1)
End Sub

End Class

Obviously when an instance of MyNumericBox receives focus, ShowIM(1) gets called but what exactly does this call in "coredll.dll"?

TIA