LoadRunner is a testing tool that load tests the application by emulating an environment in which multiple users work concurrently. While the application is under load Loadrunner accurately measures monitors and analyzes a system's performance and functionality.
HP LoadRunner software is an automated performance and testing product from Hewlett-Packard for examining system behaviour and performance, while generating actual load. HP acquired LoadRunner as part of its acquisition of Mercury Interactive in November 2006. HP LoadRunner can emulate hundreds or thousands of concurrent users to put the application through the rigors of real-life user loads, while collecting information from key infrastructure components (Web servers, database servers etc.) The results can then be analyzed in detail, to explore the reasons for particular behavior. HP LoadRunner is sold as part of the HP IT Management Software category by the HP Software Division.Consider the client-side application for an automated teller machine (ATM). Although each client is connected to a server, hundreds of ATMs may be open to the public. During peak times — such as 10 a.m. Monday, the start of the work week — the load may be much higher than normal. In order to test such situations, it is not practical to have a testbed of hundreds of ATMs. So, one can use an ATM simulator and a computer system with HP LoadRunner to simulate a large number of users accessing the server simultaneously. Once activities are defined, they are repeatable. After debugging a problem in the application, managers can check whether the problem persists by reproducing the same situation, with the same type of user interaction.
LoadRunner is a load testing tool that facilitates load testing against application thus determining the behavior of the application (server and network) when under normal load, stress or prolonged testing depending on the objective of the load test.
It basically generates no of virtual users to help you increase the load on the application to perform performance testing