How loadrunner Works?

Unlike a
WinRunner workstation which emulates a single user's use of a client, LoadRunner can emulate thousands of Virtual Users.
Load generators are controlled by VuGen scripts which issue non-GUI API calls using the same protocols as the client under test. But WinRunner GUI Vusers emulate keystrokes, mouse clicks, and other User Interface actions on the client being tested Only one GUI user can run from a machine unless LoadRunner Terminal Services Manager manages remote machines with Terminal Server Agent enabled and logged into a Terminal Services Client session.
During run-time, threaded vusers share a common memory pool. So threading supports more Vusers per load generator.
The Status of Vusers on all load generators start from "Running", then go to "Ready" after going through the init section of the script. Vusers are "Finished" in passed or failed end status. Vusers are automatically "Stopped" when the Load Generator is overloaded.
No additional license is needed to monitor standard web (HTTP) servers (Apache, IIS, and Netscape).
To use Web Services Monitors for SOAP and XML, a separate license is needed, and vUsers require the Web Services add-in installed with Feature Pack (FP1)