When you're browsing a site and you like it, you bookmark it. Right? That link gets saved into the bookmark folder of your browser, which is only accessible by you. That bookmarked site is private

1. What is social bookmarking and its benefits?
When you're browsing a site and you like it, you bookmark it. Right?
That link gets saved into the bookmark folder of your browser, which is only accessible
by you. That bookmarked site is private.
(Courtesy: SEOclerk)
Social bookmark is exactly like that ONLY instead of your browser, you're
bookmarking a site online. And it's not private but rather public, accessible by
everyone.
That is social bookmarking.

2. (Courtesy: Income Learner)

3. There are many websites/platforms that let you bookmark your favorite sites and let
others find them.
Some of the top and popular social bookmarking sites are:
1. Pinterest
2. Mix (Earlier: StumbleUpon)
3. Digg
4. Reddit
5. Scoop.it
6. Dribble
7. Slashdot

4. (Courtesy: Begin Dot)
Traditional social media platforms, too, at times, are recognized as social
bookmarking sites. Like Twitter, LinkedIn and even Facebook. Not that they help you
bookmark your favorite pages; they just make your shared content discoverable to a
lot of people.
Now each of these social bookmarking sites come with their own unique interface
and features. However, the majority of them provide enough options (including

5. tagging) to properly categorize your content/link in the right groups. This helps other
people discover that content by going in the right categories.
Social bookmarking is a prevalent practice in the SEO community. Although it is now
highly ineffective. Aside from the top names (Pinterest and Reddit), very few people
really visit the traditional social bookmarking sites.
SEOs regularly bookmark their sites and content on these platforms so to get
backlinks. That's its biggest benefit. Organic content discoverability is at its all-time
low.
So, in short, social bookmarking is nothing but a vanishing practice, left with not many
benefits.
Hope this answers your question
What is social bookmarking and its benefits?