hard tag
Using the "Tag people in your post" button instead of mentioning the friend in the comment section of the post on Facebook. When you Tag someone using the "Tag people in your post" button it will show the post on their wall. The post will also get shown in friends of the tagged person timelines. When people Hard Tag they can cause privacy concerns and spam up your wall with posts.
Jake Hard Tagged Peter in a post. The post itself was not at all related to Peter however it still got shared on Peter's wall automatically due to the nature of Hard Tags on Facebook. Peter told Jake to just use a "Soft Tag" instead if Jake wishes to show Peter a post in the future that's not related to him directly.