The Buyer-in-Training (BIT) position at CarMax serves as the entry-level role within the Merchandising department, focusing on acquiring and managing the company's used car inventory. This role involves completing a comprehensive training program over 4-6 months, where BITs learn about vehicle basics, market analytics, and appraisal processes under the supervision of a manager. The position emphasizes customer service, negotiation skills, and the ability to make informed purchasing decisions.