When you ban somebody (this is also known as “blocking”), you will not see their posts and comments anywhere. They will not see your posts anywhere. They will see your comments in other people’s posts (but you won’t see their replies).
List of people you’ve banned is available at Notifications page.
If you’re the group admin, and you banned somebody, you will still see their posts and comments in that group. If you banned group admin, they will see your posts and comments in their group.
When you ban somebody, they are quietly unsubscribed from your feed, and you are unsubscribed from them. They cannot subscribe back and cannot request subscription to your feed.
On your “Settings” page, you can specify YouTube video or link to image file, and it will be shown to everyone who is banned by you.
When you hide somebody, you will not see their posts in your homefeed, and in aggregate pages such as “Best of” and “Everything”. You will still see their comments.
List of people you’ve hidden is available at Notifications page.
When you hide a post, it is not visible anywhere, except for direct link to the post. You can see list of posts you have hidden on “Hidden entries” page.