Suppliers create "Sell" listings for goods and services that can be sold on a recurring or repeat basis when a buyer places an order.
[Buyers can then search the "Sell" listings looking for suppliers that can provide goods or services that they need]

Buyers create "Buy" listings to advertise their interest in buying particular goods or services.
[Suppliers can then search the "Buy" listings looking for buyers who are interested in goods or services that are the same - or similar - to the ones that they can supply]

Buyers create "Cooperative Buy" listings when they want to co-operate with other buyers to source goods or services. By partnering with other companies looking to buy the same (or similar) goods, buyers can potentially take advantage of more favorable pricing due to the fact that they will be purchasing in higher volumes than they could otherwise do on their own, by aggregating their purchase with someone else's.
[Buyers can then search the "Cooperative Buy" listings looking for other buyers who have posted listings similar to their requirements so that they can join forces]

Suppliers create "One-Time Sell" listings when they have goods or services that can only be supplied "once". This type of listing is typically used to shed surplus goods, or for goods that are being closed out or liquidated.
[Buyers can then search the "One-Time Sell" listings looking for suppliers that can provide goods or services that they need]