An operational data store (ODS) is a type of database often 
used as an interim area for a data warehouse. Unlike a data 
warehouse, which contains static data, the contents of the 
ODS are updated through the course of business operations. 
An ODS is designed to quickly perform relatively simple 
queries on small amounts of data (such as finding the 
status of a customer order), rather than the complex 
queries on large amounts of data typical of the data 
warehouse. An ODS is similar to your short term memory in 
that it stores only very recent information; in comparison, 
the data warehouse is more like long term memory in that it 
stores relatively permanent information.

But in staging we are storing current as well as historic 
data. This data might be a raw and then need cleansing and 
transform  before load into datawarehouse.

Operational Data store is a subject 
oriented,integrated,current,volatile collection of data 
used to support the tactical decision making process for 
the enterprise. It is the central point of data integration 
for busienss management,delivering a common view of 
enterprise data.
In Staging Area you are carried out ETL operations as per 
your business logic in order to fetch processed information 
into data ware house.

1. ODS is close to the source. We can say it is a replica 
of source system.
While the staging area is a replica of the target DW.

2. The dimention and  fact will come into picture here in 
staging.

3. We are doing the Transformations in staging schema 
before loading it to the target.

4. We integrate different ODS source systems into the 
staging area and not in the ODS.