how does thi code do what it does?! If Not Intersect.....

I know what the result of this code is but I don't understand the terms/syntax. Can someone, explain in layman's terms what it's doing please?

If .AutoFilterMode = True Then
        If Not Intersect(.AutoFilter.Range, .Range("F18")) Is Nothing Then
            .Range("$A$18:$BQ$1000").AutoFilter Field:=.Range("F:F").Column
        End If
    End If
End With

Thanks
MissDB