Usage info
This special method is part of implementing Sign in with Slack.
As part of Sign in with Slack, this method allows your app to receive information about a user who signs into your service with their Slack profile.
Response
This method retrieves user info for a user who has previously authenticated to your service with Sign in with Slack.
Some of the fields in the response to this method are preceded with https://slack.com/—these fields are Slack-specific, and they're from the perspective of Slack. For example, https://slack.com/user_id indicates the user's ID on Slack, not on your service.
team_image_default indicates whether the image is a default one (true), or someone uploaded their own (false).