Social media has made it easy for people to reproduce your online content without permission. In most cases, it will be a simple matter of misunderstanding the law. However, in some circumstances it will be deliberate theft. Copyright law covers everything online, including content, images and videos. It's therefore important to understand what the legal situation is and how you can first identify breaches then rectify the problem.
If you regularly publish articles, images or videos online, you will probably have these stolen at some stage.