What does "baseline" mean in the context of machine learning? What does "baseline" mean in the context of machine learning and data science?

Someone wrote me:


  Hint: An appropriate baseline will give an RMSE of approximately 200.


I don't get this. Does he mean that if my predictive model on the training data has a RMSE below 500, it's good? 


  And what could be a "baseline approach"?
A baseline is the result of a very basic model/solution. You generally create a baseline and then try to make more complex solutions in order to get a better result.
If you achieve a better score than the baseline, it is good.