Lambda proxy integration question

I’ve configured an endpoint to be like this POST i/tems/{item_id}/share/facebook

handler: functions/item_share_handler.postFacebookItemShare
- http:
path: items/{item_id}/share/facebook
method: post
name: jwtAuthorizer
identitySource: method.request.header.Authorization
cors: true

Howevery I’m wondering why on the “Test” section of AWS APIG console I see that:
*a textbox to fill in {item_id} (this is expected)
*a textbox to fill in {facebook} in queryString section (I don’t understand this)

  • textbox to fill in {facebook} in headers section (I don’t understand this)

Please, someone can explain why I’m seeing that?
Thank you in advance