What do Energy Transfer partners do?

Could you please explain in detail what exactly Energy Transfer Partners engages in? I'm particularly interested in understanding the CORE activities and services they provide, as well as any notable accomplishments or projects they've undertaken in the energy sector. Additionally, how does their business model contribute to the overall energy transfer industry, and what sets them apart from their competitors? I'm looking for a comprehensive overview that captures the essence of what Energy Transfer Partners does and its impact on the market.