Load testing is to test that if the application works fine
with the loads that result from large number of simultaneous
users, transactions and to determine weather it can handle
peak usage periods.

it is used to check the processing speed with max client 
required load under client required configuration.

Load Testing is testing our application is working fine or
not iff and only iff in case of applying some sort of extra
load on it . Thats what is called as Performance test as well

Load testing is a type of performance testing, that is 
conducted to determine performance metrics of an 
Appication. This can be achived, by applying loads 
symultanious within a client expected range .

it is used to check the performance of the appl.
it is done to see how the appl responds when load is given 
by increasing the no. of Vusers and how does it handle and 
upto what extent.