Usability Testing: it is a testing to check the User
Friendly of the system.
Exploratory Testing: Due to lack of documentation, the
testing team is depending on available documents,
discussions with other in a testing team,internet Browsing,
Previous experience to understand the customer requirements,
Contacting the client or customer who specifies the
requirements.

Usability Testing:Testing the user friendliness(look & 
feel) of an application.
Exploratory Testing:When there is no sufficent 
documentation about the application,we need to understand 
the application,write testcases & execute the testcases.
i.e,Exploring the application.

Usability Testing: Test the user friendliness of the 
application that is the GUI of the application.

Exploratory Testing: It is an informal way of 
testing,without any formal test documentations. The tester 
no need to know the application under test, while testing 
the tester will come to know the functionality of the 
application.

Usability Testing- Testing done to determine the ease with 
which a software application is 1)Easy to Learn 2)Easy to 
Use 3) Easy to memorise. Usability Testing also involves 
testing of Aesthetic aspects of product (Look & Feel). 
Usability Testing is imporant as it demotivates the user 
from using an application.

Exploratory Testing- Type of testing in which the 
experiance of the tester is used to anticipate what defects 
might be there in the system. In this type of testing there 
is less focus on documentation & more focus is on test 
execution. This type of testing is done when there is no 
formal Requirment Documentation exists.

usability: comfort level of the user
Exploratory: take one requirment based on that keep 
exploring the application.