How to make a vocabulary for ORB_SLAM2?
For a monocular input from topic /camera/image_raw run node ORB_SLAM2/Mono. You will need to provide the vocabulary file and a settings file. See the monocular examples above. what is the vocabulary and how to make a vocabulary ?
Apparently you are quoting from here: https://github.com/raulmur/ORB_SLAM2#... That might help people know what you are talking about.