Use dictionaries for definitions.
Some dictionaries provide paragraph length aritcles.
Not sure what a P/E Ratio is? Or how it differs from a P/B or P/S?
Look it up.
Credo Reference contains several business related dictionaries and encyclopedias. Hint: First search for your term, then limit your results to "Business" in the All Subject Dropdown Box.
Here is a list of links to dozens of specialized online business glossaries: