Content Curation in simple words is aggregation of the best content available online. This can be further paraphrased as topic related or relevant content that users find useful and entertaining. Naturally it should also be information rich since that is what wildly searched on Net - unique information.
While in Social Media we try to make our platforms like blogs, article sites, websites and forums rich in content we can not always do it ourselves. Hence in order to fulfill the content gap we usurp that which is available freely on the Internet. This is not plagiarism since the link of the site where it is published in attached to the article.
Apart from information dissemination and entertainment contents also increase online followers seeking all this. This then becomes an important marketing tool and raise brand equity of businesses.
If effectively curated the social media platform becomes a one stop shop for those seeking the right stuff. This also helps avoid long and tiring searches on the unfathomable web.
Sharing content propagated by outsiders in nothing shameful on the contrary it is wise strategy. Content curation increases versatility of what you make available and in a way increases your authority by enhancibg your grasp of the subject.
There are many tools on WWW available to sort out, choose and publish outsider contents.