What Does Subscribing Mean on YouTube?
By subscribing to a particular channel or user on YouTube, you can receive instant updates whenever new content from that source appears. It also enables you to view activity from the user, such as videos that have been named "favorites," ratings that have been given and comments that have been left. The "Subscribe" button appears next to every user name on the YouTube site, and subscriptions are managed from the Subscription Center at youtube.com/my_subscriptions.
Subscribing to a User
Subscribe buttons appear next to all the user and channel names on YouTube if you are signed into a Google account. Click the button to subscribe to a user and a confirmation window will appear. Check the box labeled "Also email me for each new upload" if you would like to receive email alerts of new activity as well as having it appear in the Subscription Center. The user in question receives an alert indicating that you have subscribed to his channel.
Subscriptions can be accessed from the Subscription Center. Click the drop-down menu next to your user name in the top right-hand corner of the screen to access it. "Subscriptions" also appears as an option alongside "All activity" and "Recommendations" on the main YouTube front page at youtube.com. From within the Subscriptions Center, it's possible to review new content from your subscribed channels, set which content appears from each user and change the associated email alert settings. The users that you have subscribed to will appear as a list down the left-hand side.
Other Users Subscribing to Your Content
If another YouTube user subscribes to your user account channel, he is able to see videos, ratings and comments that you choose to make public. They are unable to see private videos hosted on your account. To change which of your content and activity on YouTube is public, and therefore the information that your subscribers can see, visit the "Settings" link that appears in the drop-down menu beneath your user name in the top right-hand corner of each page on YouTube. Open the "Activity Sharing" link to change which activities are included in your user account's feed. This feed is accessible to anyone who has subscribed to your YouTube account.
Unsubscribing from a User
If you no longer want to receive video alerts and other updates from a user or channel on the YouTube service, you can cancel your subscription. Visit the Subscription Center at youtube.com/my_subscriptions and select the relevant user account from the list on the left-hand side of the page. Click the "Edit subscription" link next to the user name, select the "Unsubscribe from..." option and then click "Update" to confirm. The selected user account will be removed from the list of entries on the left, and you will be returned to the main Subscriptions Center page.