This is why barter continues to be used, thousands of years after money was invented. Later in this article I'll attempt to explain why barter is often preferred to the use of money. However, ordinary two-way barter is less flexible than money. But I don't want ten dental checkups. I want my roof repaired.
Multilateral barter retains the advantages of barter, but adds an element of flexibility.
Multilateral barter is barter among 3 or more people. For example, A, B and C can make a deal where A does gardening for B, B does cooking for C, and C gives A a good used bicycle. Simultaneous means that all three people agree to the deal at the same moment. The goods may be delivered later, but the decision to trade the various items is made at a single time. Ordinary two-way trading is usually simultaneous.