There are two types of system prevalent for Commodity Trading:
Order Driven Market / System
This Trading system allows the users to enter both Buy & Sell Orders, and matching is done on Price & Time priority basis. The orders are first matched based on Price, and if there are two orders at the same price, the first order would get priority in matching over the second order. An order may match partially with another order resulting in multiple trades.
Conventional Auction Market / System
A system where potential bidders place competitive bids on commodities and assets and at the end, best bid wins the auction. This is a conventional system of Trading at APMC with which all Physical Market participants are familiar.