Is there any rules set by default if no rules is set for PMD?

I have a question. Im trying to create some rules with the PMD tool and test my code. It gives violations when I set rules in my .xml file. But when I remove all rules or outcomment (no rules set) it still gives violations as if there is some default rules set. Does anyone have any clue how it works? Please give me feedback since I need to figure this out. Let me know if you want anything else to help you answer it!