The feature lets you filter or annotate the search results by reading level. The reading levels include basic, intermediate and advanced. You can either have Google label or annotate the results with those labels, only show basic results, only show intermediate results or only show advanced results.
At the time of writing, slashdot is 1 % advanced, 64 % intermediate and 34 % basic.
What do they even do?
Since they reject $45 billion takover bids, they must have a plan.
Never invest your money in anything that eats or needs repainting. -- Billy Rose