你是那个amazon prime shipping trial 吧.
shipping on purchases 就是你消费的物品的运送.你断句断错了,所以没法理解
It's $79 a year that gave its users free two-day shipping on purchases and access to Amazon’s free instant,
这是个79美元/年的送货服务,免费（交完钱不加其他费用）两天内送到的你购买货物,而且这亚马逊的服务即时生效（花了钱就能立马生效）.
streaming video library.
streaming video(应该是流媒体的意思)图书馆.