client server is 2 tier architecture ,in this case 
application is deployed in client machine and database is 
on server for examples applications in foodworld/medical 
shop etc.Here both the presentation and business layer are 
in client machine whereas database in server machine.

web-based is 3 tier architecture ,they are three layers 
those are presentation layer,business logic and data logic 
in presentation layer browsers are installed ,in business 
layer web server/app servers  are installed and in data 
logic  database servers are installed for ex yahoo server
through browser we type the url(www.yahoo.com) which will 
hit the yahoo server which is business layer if any data it 
has to access it will get it from database layer.

Client server appliction is two tier, like the client
(application) wil be in one machine and the server
(Database) will be in another machine.In this the client 
performs major tasks lke monitoring and manipulating and 
server is used for storing database.

Where as a web based application is three tier. It will 
have three parts such as front end screen, webserver and 
database. here frontend only maonitors means takes input, 
webserver manipulates the data and database stores the data.

Client server architecture:Here CLient will be having
presentation layer and server will be having business and
database layers.Client can send a request using presentation
layer and can get the response from the server
testing the above applications are called client server testing
web based application: here different clients will interact
with different servers and clients will be having
presentaion layer and business layer and database layers
will be distributed across different servers.client can send
a request using web browser and application server which has
the business logics will interact with database server and
it gives the response.
testing the applications in the above architecture are
called webbased testing