Directly from Microsoft Learn Select an availability test – Training | Microsoft Learn:

• URL ping test (classic): You can create this test through the portal to validate whether an endpoint is responding and measure performance associated with that response. You can also set custom success criteria coupled with more advanced features, like parsing dependent requests and allowing for retries.
• Standard test (Preview): This single request test is similar to the URL ping test. It includes SSL certificate validity, proactive lifetime check, HTTP request verb (for example GET, HEAD, or POST), custom headers, and custom data associated with your HTTP request.
• Custom TrackAvailability test: If you decide to create a custom application to run availability tests, you can use the TrackAvailability() method to send the results to Application Insights.