The basic characteristics of client/server architectures 
are:

1) combination of a client or front-end portion that 
interacts with the user,and a server or back-end portion 
that interacts with the shared resource. 
The client process contains solution-specific logic and 
provides the interface between the user and the rest of the 
application system. The server process acts  as a software 
engine that manages shared resources such as databases, 
printers, modems, or high powered processors. 

2) the front-end task and back-end task have fundamentally 
different requirements for computing resources such as 
processor speeds, memory, disk speeds and capacities, and 
input/output devices. 

3) the environment is typically heterogeneous and 
multivendor. The hardware platform and operating system of 
client and server are not usually the same.Client and 
server processes communicate through a well-defined set of 
standard application program interfaces (API's) and 
RPC's.

4) An important characteristic of client-server systems is 
scalability. They can be scaled horizontally or vertically. 
Horizontal scaling means adding or removing client 
workstations with only a slight performance impact. 
Vertical scaling means migrating to a larger and faster 
server machine or multiservers.