Manual spot bidding involves the traditional process of carriers and shippers negotiating and agreeing on the rates for transporting goods on a case-by-case basis, while smart spot bidding utilizes technology and data analytics to automate the bidding and selection process for spot shipments via platforms that connect shippers with carriers and use algorithms to optimize the bidding process based on various factors, such as shipment details, carrier capacity, historical performance, real-time market conditions, and even predictive analytics.