CLIENT:it is nothing but only one user can access it
SERVER: it is nothing but multiple clients can use this 
server

A client is defined as a requester of services and a server 
is defined as the provider of services. A single machine 
can be both a client and a server depending on the software 
configuration.

server nothing but a computer that delevers instaction's and
software to other computer's through network

client nothing but a computer it accept all instation from
server.

Client requests the information and Server provides the 
information.
AN application will have Presentation logic, Bussiness 
logic and Database logic.

In Client Server environment, Client carries Presentation 
Logic and Bussiness Logic and Server contains Database Logic

In Standalone Environment, a single machine can be both 
client and server.

In Web Environment, Client carries Presentation logic, 
Application Server carries Bussiness logic and Database 
server carries Database logic