Help
Help browser for GNOME
Yelp is the GNOME help viewer. It is the default Mallard viewer, but it can also display DocBook, info, man, and HTML documentation.
It makes it easy to find the documentation you need, with interactive search and bookmarks.
It also has an editor mode, which shows editorial comments and revision statuses when editing Mallard documents.
Yelp is the help browser for the GNOME desktop. Yelp provides a simple graphical interface for viewing DocBook, Mallard, HTML, man, and info formatted documentation.
How to install Help in Ubuntu
If you are on a supported distro, you can install the application through software center by clicking the below link.
If the above link not working, run the below command in terminal to install yelp in Ubuntu
sudo apt install yelp