What are "ie.readyState" and "ie.Busy" for ?

Hi forum experts,
Can someone explain me that what are the following codes used for ?

Sub Macro1()
Set ie = CreateObject("InternetExplorer.Application")
ie.Visible = False
ie.Navigate ("http://www.excelforum.com")

Do While ie.Busy
DoEvents
Loop

Do While ie.readyState <> 4
DoEvents
Loop
End Sub

Sub Macro2()
Set ie = CreateObject("InternetExplorer.Application")
ie.Visible = False
ie.Navigate ("http://www.excelforum.com")

Do Until (ie.readyState = 4 And Not ie.Busy)
    DoEvents
Loop
End Sub