If someone is using maven project he/she will definitely encounter setting.xml file.It is a place that contains configuration , proxy,repositories,authentication , passwords etc..
Right Click pom.xml -> maven -> open settings.xml
What is the use of settings.xml??
The user level will allow configuration which should not be bundled to any specific project, or distributed to an audience. These include values such as the local repository location, alternate remote repository servers, and authentication information.
It is totally different than pom.xml in the sense that settings.xml is user preferences.I have used it for getting access to certain artifact which needs authentication,server access passwords and ids and some file and directory level permission
More details : https://maven.apache.org/settings.html