Column Headers?

No. If you put some garbage in the textarea of the import and import it, you will get an error message with the list of all the columns but there is no description.
The names are pretty straight forward though...
product_weight : weight of the product
product_weight_unit : weight unit for the weight of the product
product_quantity: quantity of the product
product_id : id of the product
price_value: price of the product
price_currency_id: currency of the price of the product
...etc...

We didn't feel like such description would be useful since the names are already self explaining. If you have a precise question of a field, you can always ask and we will answer you...