It would help to post a screen shot so we can see what you are talking about.
The default number of audio and video tracks is 3. If you have more, you would have had to have added them at some time. Next time you create a new sequence, check to see if you are using a custom preset. It's possible you are using one with additional audio tracks. You can check the number of tracks in in "track" tab of the new sequence dialog.
You can also get additional audio tracks by adding them while editing. You can explicitly add additional tracks, or you can indirectly add them by dragging and dropping a clip on the timeline in the black area above the top track.
As for the separation of audio and video, it's hard to know what you are talking about without a screen shot, but it could be entirely normal. When you add a clip with audio and video to the timeline, the video will go on a video track and the audio will go on an audio track. The timeline is divided horizontally into two sections with video tracks on the top and audio tracks on the bottom. The only time the audio and video tracks are together is when you are working with track one. If you are working with multiple tracks, the audio tracks will be placed in the audio track section on the track corresponding to the one you placed your video track on.
tracks1.JPG
The audio and video tracks for a clip are linked together, if you move the video track to another position along the timeline the audio track also moves. But, they don't move together if you move from one track to another. They are independent in that regard -- move one, the other stays. This is also a way to introduce gaps between the audio and video.
You do not have the required permissions to view the files attached to this post.