A video with a lock symbol is a part of the Show Pass offer. If you click onto the lock symbol then it will bring you to the Show Pass page for subscription. If you wish to watch that video, you may either purchase the video or subscribe to Show Pass to gain access to that video and up to 84,000 other videos.
A video with an unlock symbol is also a part of the Show Pass offer. However, the unlock symbol means that you are subscribed to Show Pass and you have access to that video and as many as 84,000 other videos. No payment is necessary to watch any videos with the unlock symbol.