Break connection between drawing and a part

Hi

I have a drawing connected to additional part.

When I open drawing M168.000.000  it open also PART 168.30.01.a.SLDPRT.

  • The drawing and the part are different and I don't know how and why they become connected.

1-  How can I break this connection ?

2 – What is the purpose of this kind of connection ?

SolidworksDrawings And Detailing