i) Extraction : - Extracting the information from different sources i.e. different databases. 

ii) Transformation :- Transformation is said to be applying the logic on the extracted data from sources.    

iii) Loading :- After applying the logics on the source data, we will deploy it to the target systems which is said to be Loading.

2) A good ETL tool must be able to communicate with the many different relational databases and read the various file formats used throughout an organization. ETL tools have started to migrate into Enterprise Application Integration, or even Enterprise Service Bus, systems that now cover much more than just the extraction, transformation and loading of data. Many ETL vendors now have data profiling, data quality and metadata capabilities.

3) The following are the ETL tools.   

i) Informatica   

ii) DT/Studio 

iii) Data stage 

iv) Ab initio   

v) Data Junction 

vi) OWB 

vii) MS SQL Server Integration

viii) Transform on demand 

ix) Transform manager

2) Informatica is an easy to use tool in which we just need to drag and drop different objects (known as transformations) and design process flow for Data extraction transformation and load. These process flow diagrams are known as mappings.

3)Once a mapping is made, it can be scheduled to run as and when required. In the background Informatica server takes care of fetching data from source, transforming it, and loading it to the target systems/databases.

4)Informatica can communicate with all major data sources (mainframe/RDBMS/Flat Files/XML/VSM/SAP etc), can move/transform data between them.

5) It can move huge volumes of data in a very effective way, many a times better than even bespoke programs written for specific data movement only. It can throttle the transactions (do big updates in small chunks to avoid long locking and filling the transactional log).

6) Informatica can effectively join data from two distinct data sources (even a xml file can be joined with a relational table).

7) Informatica has got the ability to effectively integrate heterogeneous data sources & converting raw data into useful information.

2) DT/Studio’s well-developed feature set, which Embarcadero borrows from its other products, like ER/Studio.  DT/Studio lets users move data from multiple sources to any location or application in three steps:

i) Using ER/Studio, the tool reverse-engineers the existing operational data 
ii) DT/Studio transforms the data from the original source into the user stablished data format.
iii) It populates the target or application at the optimum speed required