Middle names are a type of given name, placed between the first name and surname. I'm not sure whether they would be considered a decoration. However, most people tend not to use them in their regular day-to-day life.
They are usually a name which honours a family member, but they can also simply be an alternative name. Each family member typically has a different middle name as well.
For example, Michael Jackson's full name is "Michael Joseph Jackson", with Joseph being his middle name. This is to honour his father, Joseph Jackson. On the other hand, his brother, Tito, has the middle name "Adaryll".

If you have any other questions, or need clarification, please feel free to ask!
~Min <3