The one on the left is your source track patching indicator and the one on the right is the sequence track. If you have a video clip loaded into your source monitor (left) then you will get a corresponding V1 patching icon at the left of the timeline. You can use this to determine which sequence tracks you want to edit your clip onto.
Try this to get a hang of it. Load a video clip into the source window, activate the source patching icon next to (say) video track three (V3), hit the period key and that clip will be inserted into your sequence in the V3 track where you currently have your timeline indicator. And if you have set in and out points to the clip ('i' and 'o' keys) in the source window first - only that part of the clip will be inserted into the sequence. The timeline indicator will also jump to the end of that clip ready for you to insert the next clip in the same way - quick and easy way to start assembling your edit.