Social Bookmarking:
It can be co-related with bookmark option available in our browser where we save/bookmark the link to get easy access.
Similarly, we bookmark website links on bookmarking platforms. The only difference here is a group of people can see the links you have shared which will help in increasing traffic towards your website. Example websites include Diigo, Cheezburger, Stumbleupon, Reddit, etc.
Social Networking:
Through social networking, we communicate with our network over various social media websites like Facebook, Twitter etc. Here we do not spread our website links because it is considered spam and your account may get blocked.
Hence, SMO is posting content on social media networks advertise yourself in order to generate leads.
After uploading the post, you have a specific link. Promotion of these links on bookmarking websites is known as social bookmarking. So, bookmarking is also a part of SMO.