1.  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.

2. stress testing often refers to tests that put a greater emphasis on robustness, 
availability, and error handling under a heavy load, rather than on what would 
be considered correct behavior under normal circumstances. In particular, the 
goals of such tests may be to ensure the software doesn't crash in conditions of 
insufficient computational resources (such as memory or disk space), unusually 
high concurrency, or denial of service attacks.