Which Traffic Source dimensions does Google Analytics automatically capture for each user who comes to your site?

Google Analytics automatically captures Source, Medium, and Campaign name as key Traffic Source dimensions. Source identifies where the user came from (e.g., google, direct, facebook.com). Medium describes how they arrived (e.g., organic, cpc, referral). Campaign name is used to identify a specific marketing campaign that brought the user to the site. While Keyword can be a valuable dimension, it is primarily captured for paid search traffic and isn't universally captured for all traffic sources, making "Source, Medium, Campaign name" the most accurate and comprehensive set of automatically captured dimensions among the choices.