what is this function in timeline panel (V1 V2 V3.....)

[manpilfer]

I am sorry for my bad English,

I have no idea about V1 V2 ..../ A1 A1 for what? how to use that?

when enable/ disable but nothing happen

What is different front and back function between locking sign

Please , help me find out

Thank you in advance

[Meg The Dog]

The buttons on the left are Source Patching, the buttons on the right are Track Targeting:

You can learn about what they do here:

https://helpx.adobe.com/premiere-pro/using/source-patching-track-targetting.html 

MtD