Complex sentence: It lies at the western end of Amazonas state, next to the border with Loreto Region, Peru, and derives its name from Javari River, which is the most important of the region (thus the name "Javari Valley").
Split into simpler sentences: It lies at the western end of Amazonas state, next to the border with Loreto Region, Peru. It derives its name from Javari River, which is the most important of the region (thus the name "Javari Valley").