I have used the following request link to extract data using Stack Exchange API. But I have no idea how to create "filter" as used in the request line.

Please help me understand creating of such filter in order to get the desired fields in response.

https://api.stackexchange.com/2.1/users/2/answers?key=xTr7YgsHdmfcevW6Vo1\*BQ((&page=1&pagesize=100&order=desc&sort=votes&site=stackoverflow&filter=!3u0zcO%28lpHVEGuskA