this environment contains two tiers one is for cleints and 
the other one is for server.
presentation layer and business layer will be present in 
the clients and database layer will be present in the 
database server.

when ever the application need to be used in a single place 
like single building a single organization or in numbers of 
branches in single cities and if the application need to be 
accessed very fastly then the environement sugusted is 
client server environment or two tier environment.

Three tier environment: This environment containsthree 
tiers, one is for cleints, the middle one is for the 
application server and the last one is for database server.

Presentation logic will be present in cleint business logic 
is present in the application server and the data base 
logic is present in the database server.

when ever the application need to be used all over the 
world by limited number people when the environment is 
suggested is web environment or three tier environment.