When you have a post you want to bring to the attention of others, you can use the Sharing Knowledge feature. On the other hand, when you have a plan/idea that you want others to participate in (possibly) or you would like to see it implemented, you use the Sharing an Idea feature. Sharing Knowledge and Sharing An Idea posts differ in that, you can like knowledge posts and on the other hand you can upvote/downvote Idea posts to show that you are interested or disagree with the idea.

Only Admins can mark an idea as implemented from My Work-Space --> Idea Share. Its the Admins who decide whether an idea holds value for consideration to be implemented.

You can read more about social posts here at https://engagedly.com/social/