I have an exiting farm and I wanted to make a new server join the farm , I installed the same version and prerequisites needed and all is good . My question is, when I launched the central admin of the new server I found the same web applications and data exiting although I didn't do any restore yet . Can any one explain what did happen here ? I searched a bit but I couldn't understand .
Thank you
When you installed and ran SharePoint Products Config it would have asked you if you were joining to an existing farm, and then it would have asked you for the database server and name. This is where it is getting all the information from. You don't need to do a restore - it uses the same database server and config database.
For further config details, see this blog post: https://stevegoodyear.wordpress.com/sharepoint-2013-build-guide/joining-additional-sharepoint-servers-to-the-farm/