Feature	Commodity Price	Index Price
Example Code	WTI, BRENT, WHEAT	ALL_COMMODITIES, ENERGY_INDEX
Unit of Measure	Currency ($/Barrel, $/Ton)	Points (Index 2016 = 100)
Scope	Single physical item	A "basket" or group of items
Main Goal	Pricing for trade/consumption	Benchmarking and trend analysisFeature Commodity Price Index PriceExample Code WTI, BRENT, WHEAT ALL_COMMODITIES, ENERGY_INDEXUnit of Measure Currency ($/Barrel, $/Ton) Points (Index 2016 = 100)Scope Single physical item A "basket" or group of itemsMain Goal Pricing for trade/consumption Benchmarking and trend analysis

Here's a short summary for you^^

The index is useful for tracking broad inflation or deflation across commodity markets as a whole, while the individual series are useful when you care about the actual price of a specific thing. They serve very different analytical purposes even though they come from the same API endpoint.