Amazon river is used for many different things today, for example it is a soure of over 3,000 types of fish, which is a great food source. It is also used for travelling, or delivering food and other goods to different cities or places. It also expands the biodiversity of the rainforestst.
The Amazon River was placed there for the purpose of draining water from thousands of streams and rivers all across South America, and of providing habitat for the thousands of species of insects, birds, fish, lizards, and plants that live in or near it.
Recently, since the advent of homo humanus ... a unique species that's always looking for a way to "use" nature ... the river has begun to be used as a source of water for farming and drinking, as an easy source of protein, and as a transportation route.