If you are in one of those areas with Taobao forwarding service, you don't need an agent. You can just order it on Taobao and they will ship it to you. These places include HK, Taiwan, S.E. Asia, Australia and NZ. Since you are not, you have to order it using some kind of agent service - MisterTao for example. In most case, AE seller are like agent as well. They just resell Taobao's stuff + extra fee.