The pearls in the picture are likely the first option (gem quality) that is out of stock. The pictured pearls in the picture have good color and medium luster - although the luster may be better but with the photography it is hard to tell.
The second option, from what I understand from the description, is what we would call pearls with a clean face. This means that the front side of the pearl is clean, but there is blemishing on the sides or back.
When buying pairs of Tahitian pearls or making pairs of Tahitian pearls a lot of wholesalers will match pearls with clean faces but blemishing on one side. It is a good option to bring the cost down on a pair of pearls. These types of pearls are used extensively in pieces with large cups (like pendants) that will cover the majority of the blemishes. In graded lots these pearls would likely fall in the A/B to B range (using Tahitian A-D) or AA+.
This is what I see based on the description and details. It is difficult to be certain, however, as the Web site lacks a grading page that explains the criteria in detail, and the items themselves lack this too. That does not mean there is anything wrong with them, however.
Here is a link to our
Tahitian pearl grading page that explains the same thing.