The yellow balloons or boxes you see are default. They show the description of the file. eg: mp3 id3 tag information or movie description, etc. Not all files have a description, but most people add them because it helps the file to be found in searches & also supplies more identifying information so a person knows if it's different to another of same name, etc. (eg: song length)

There are also some that belong to the program. For example if you hover your cursor over the Library window download folder / Saved Files folder then it will show the directory location of that folder.