Before Enron collapsed, what type of business were they? What did they do to make money?

Answer 1

Enron was basically dealing in Natural Gas, Natural Gas liquids, electricity, exploration and producation, operater of power plants and natural gas pipelines.

Answer 2

Here is a great series that was produced by the National Public Radio (NPR). It gives details on the exact business ventures that Enron was particpating in and what utlimatly led to its (and Ken Lay's) demise.
http://www.npr.org/news/specials/enron/
The link below is to Enron's website. It is basically just there to distribute information about the $billions in debt that need to be paid by/for Enron.