ACID property related to transactions
i.e client server communication is called transaction.
A transaction is a sequence of operations performed as a 
single unit of work.A logical unit of work must exhibit 
four properties called ACID(Atomicity,Consistency,Isolation 
and Durability)properties to qualify a transaction.

Atomicity:A transaction must be an atomic unit of work.i.e 
either allof its  data modificationsare performed ,or none 
of them is performed. 

Consistancy:when trasaction completed it must leave all data
in a consistant state.

Isolated:Modifications made by current transactions must be 
isolated from the modifications made by other trasaction.

Durability: after  transaction has completed ,it's effects 
are permanently in place in the sytem.