Shader Blending OneMinusSrcColor etc

Hi, I am newbie in shader, and now i am learning it.I am learning the basic syntax now, and stuck in Shader Blending, i am not clear about the official document's description: http://docs.unity3d.com/Documentation/Components/SL-Blend.html,especially in SrcFactor DstFacto and the Properties: OneMinusSrcColor etc. Can you describe this for me or make a pic to show how it works? Any answer will be appreciated! Thank you!