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.