Would someone care to explain to me, in brief, what this tool is used for?

Things you might want to include in your answer:
Scenarios: Symptom + process + result
Basic run command usage
Most commonly used for...
+anything else you deem relevant 

Keep in mind, I don't need in depth explanations for the coolest features, I would like a simple 1-2 paragraph explanation of where this tool gets used the most and the process(es) involved in using it most effectively.
Thank you