Learning the application and testing the application in the
absence of the requirements / reference document is said to
be Exploratory testing.It can also be known as adhoc testing.

Adhoc Testing or Monkey testing

It can also be known as adhoc testing.
Due To lack of test data test engineers are conducting
testing on application build based on their experience
discussions with other and get requirements from the client.

exploratory testing is testing the application without 
using baseline documents and also without the knowledge of 
the application.

Exploratory testing should be done when there are no poor 
specifications with less planning and minimum documentation.

To identify defects by experience based technique with 
skilled person having good domain knowledge,Testing skills 
and knowledge in database.

To explore the application and find new defects which are 
missed during system testing phase.

Exploratory testing is the kind way testing we are
conducting without having any needful documentation of
application.Here we can do testing based on the previous
related documents or based on the past exp or taking help
from the senior testers.

Its a kind of testing conducting at the time of 
documentation lacking.
In the testing process whenever we dont have sufficent 
documentation to do the testing process like preparing test
scenarios,test cases then we will go for the follwoing 
techniques.

1)getting information from the previuos projects
2)taking suggestions from the seniors and leads or managers