Question problem with receiving data from Rs232

[dxtr]

i made a small program that allow reading rada from Rs232 , but i have problem with this function :

Private Sub SerialPort1_DataReceived(ByVal sender As Object, ByVal e AsSystem.IO.Ports.SerialDataReceivedEventArgs) Handles SerialPort1.DataReceived               Label8.Text = SerialPort1.ReadExisting()    End Sub

i got this

Cross-thread operation not valid: Control 'Label8' accessed from a thread other than the thread it was created on.

whats "Thread" and how can i solve this problem
srry for my bad english