The Scores that are displayed in Leap are based on both Lab and Field data.
What is the difference between Lab data and Field data?
Lab data is artificial and collected from a single, predefined device, location, and internet connection. This is a useful test for getting an initial idea of your site’s performance when testing but will not necessarily be an accurate reflection of how all your users will experience your site. Some Lab data tests can also be affected negatively by the testing environment, for instance some tests that use Lab data can be impacted by external factors such as active web extensions or poor internet connection.
Field data is gathered from many users, and you can filter it to focus on a specific user and their experience. This is much better for getting a “real world” impression of how users will experience your site and because you can target specific scenarios with Field data allows for you to target your testing. The disadvantage of Field data is that it takes a long time period to gather accurate and reliable data since the more users that you can test the better the results.
Field data is what google uses to measure page experience, this applies to core web vitals and is an important factor that google uses to rank sites. Leap is able to track your field data by pulling data directly from Google CRUX data (the same data they use for field scores in page speed insights).