Hello,
The conjunction И extremely and widely used in Russian, and it has lots of cases when comma should follow by И, or before, or even both together.
В комнате стояли столы, стулья И полки. - nothing more (but there should be a context - either nothing more from furniture, or nothing more literally) - but the accent is made for a limited number of things. it is the most used way even if there are other things (Russians will never thing of such complicated things in grammar) - it is 100% correct too even if there is something else
В комнате стояли столы, стулья, полки. - the list could continue but the most important that will bring understanding is that the room is not empty and quite heavy and large objects are there.