This does ESM (which they call state space since they are a form of state space models). The function es chooses the best model amongst 30 possible ones. But I can not find a list of which 30 it chooses from (they provide generic information about the type of model but I am trying to compare these to known ESM models like say Holt).
This is the documentation https://www.rdocumentation.org/packages/smooth/versions/2.6.0/topics/es
This is the documentation https://www.rdocumentation.org/packages/smooth/versions/2.6.0/topics/es