Client server: 
       1.Application and server will be there.
       2.if we want data we will send a request to server
directly.
       3.Server will fetch data and send to application.


Web based System:

       1.Application, Middleware and server.
       2.if we sent data request, request will go to
middleware from middleware to server.
       3.Response will come from server to middleware and
middleware to application.

       4.we r not authorised to connect dirrectly to server(
mailnly for security ) ex: Yahoo

Client server system refers working with intranet

whereas 

web based system means working with internet.