Load testing:opening no if webpages at a a time and 
checking how the system reacts.

stress testing:opening no of webpages at aa time and 
minimises the resources like RAM,etc so that stress should 
be created at a time and observe how system reacts to this 
condition.
that is what i have been taught in the class.

Load Testing: Testing the application under heavy but
expected(known) load is called load testing.

E.g.: If a chair is capable of bearing 100 K.g. weight, then
for load testing, we put 100 K.g. weight on the chair and
observe the behavior of chair with expectation that chair
will be capable of holding 100 K.g..

Stress Testing: Testing the application beyond its
specification and determine the response of the application
in terms of where application degrades or fails.   

E.g.: Put weight of 101 K.g. on the chair and see behavior.
Also continuously increase weight on chair and observe where
it fails to bear load.