1.They are process which run when a request is made by client. Handlers include extension like (.aspx,.ashx).
2.We can implement custom Handler by implementing IHttpHanlder (ProcessRequest and IsReusable method)
Life cycle of HTTPHandler is only till the request is made.
1.They are events which can be used even before page load /request is made to the server. 2.HTTP Module can be used for the entire life cycle of MVC where as HTTPHandler is valid only for handling request.
3.We can implement custom Module by implementing IHTTPModule(Init and Dispose Methods)