In Apache JMeter, how can one simulate different types of browsers or devices in a load test?

In Apache JMeter, simulating different types of browsers or devices in a load test is achieved by using user-agent strings. User-agent strings identify the type of browser or device making the request to the server. By customizing these strings in JMeter, testers can emulate various browsers and devices, allowing them to assess the application's performance across different user environments. This is crucial for ensuring compatibility and optimizing user experience.