The small porous clay grains store water like a sponge. So plants in Seramis can be watered 3 times less frequently than those in soil. The roots grow into the porous surface of the clay granules taking as much water and fertiliser as they need.
Soil can rot and consolidate which hampers the airing of the roots. If the roots don't get enough oxygen they die. Seramis clay granules however keep their structure, apparently, they don't grow old or consolidate so roots are always perfectly supplied with oxygen.
Now, I don't have a, "green thumb" for indoor potted plants and I've never used this product before, but anything that can help make the up keep of such plants simple is a winner in my book. And speaking of simple, take a look at one of their outdoor ad campaigns.
This takes the idea of healthy plants to an extreme but it makes a direct link between the company name and the idea of large, healthy plants.