Question: i just need to know what happens when you create a RSS feed in Liferay?
Is the configuration data for the feed (Structure, template, friendly url of the portlet...) stored on the DB or in a file?And, in both cases, where the data is stored exactly?

Answer: 
they are stored in the DB, if anyone is interested!
Update: i will detail the answer more if anyone is interested. They are stored in the table JournalFeeds.
In liferay RSS feed are stored under **web content** in a **feed** tab You can display these feeds using rss portlet.