Spring MVC is the standard MVC solution provided by SpringSource for your web applications , so you have the concept of a view which is for example your JSP page , a controller class (annotated with @Controller ) and a model which represents your data.
Spring Webflow is built on top of Spring MVC and differs slightly in purpose although it inherits most of the features of Spring MVC , webflow is more suited for wizard style applications where you enter data on a form and that has to pass a series of validations or capture of number of additional data on different pages before you complete your business process.
a. trying to decide which one suits your use case b. asking from a client request perspective - in an MVC paradigm a request travels through a controller, gets updated with something from the model and ends up at the dictate View. - in a web flow paradigm a request may go through various paths and views depending on the rules. Credit card processing is a simple example of a paticular web flow.