HTTP Handler :
HTTP handlers are the .NET components that implement the System.Web.IHttpHandler interface. Any class that implements the IHttpHandler interface can act as a target for the incoming HTTP requests. HTTP handlers are somewhat similar to ISAPI extensions. One difference between HTTP handlers and ISAPI extensions is that HTTP handlers can be called directly by using their file name in the URL.
HttpHandler is a extension based processor.
HTTP Module :
Http modules are called before and after the http handler executes. Http modules enable developers to participate in, or modify each individual request. Http modules implement the IHttpModule interface, which is located in the System.Web namespace.
HttpModule is event based processor.
