What distinguishes a JavaBean from a Servlet?
JavaBeans are a set of rules to follow to create reusable software components, or beans. This contains properties and events. At the end you have a component which could be examined by a program (like an IDE) to allow the user of your JavaBean component to configure it and to run in its Java programs.
Servlets are Java classes running in a Servlet engine implementing a particular interface: Servlet, forcing you to implement some methods (service()). The servlet is an extension of your web server where this servlet is running on and only lets you know when a user requests a GET or POST calls from a web page to your servlet.