Helium 10's tools try to make it as easy as possible to understand what the different types of data mean inside the tools.
To help users, the tools are populated with little tooltips. Wherever you see a small circle with a question mark in it, you can place your cursor over the circle, and the tooltip will open with a brief explanation.
Also, if you hover your cursor over the title of column headings, the explanation of that data will display for you.
Finally, this Knowledge Base has a Serious Sellers Glossary to help you with unfamiliar terms.