 view row styles a row style is an individual style to display only an individual record within a view for example a node type view would display one node per row a user type view would display one user per row some row styles use fields which means you select from the available fields to display others do not they are able to use the base type and create a display usually row styles that do not use fields produce less efficient slower views  so bear this in mind when contemplating the performance of your site 