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Like what is written in the picture, this notification feature can help you get new updates from every board or thread (if you enable this feature for your board you will get updates if there is a new thread and if you enable this feature in aa then you will be given know if any new people comment on the thread), then after you activate or use this feature you will get a notification to email address you used to register in BitcoinTalk.
If you want to get a new update about a bounty, then use notify feature on section board that I give the green mark on the picture.
This information is very helpful for the newbie especially for me, I have read enough other threads very informative but information like this I have not had time to read it, I am very lucky can read it now, I am very grateful for the information....