Send credentials preemptively instead of waiting for a 401 authentication challenge

Hi All,

Could someone help me the below questions?

1. I am not able to understand the meaning of "Send credentials preemptively instead of waiting for a 401 authentication challenge" while creating Integration using HTTP from Scratch. Could you please make me understand in simple terms.

2. I need few free URLs for GET and POST to create Integration for Learning and Free WSDL Url to integrate inside of a Process Model.