It's a super small, chemically chopped up version of sodium hyaluronate. Its trade name is miniHA, and its molecular weight is 10 kDa. This counts as really tiny given that "normal" HA has a molecular weight of 0.5-2 million Da.
To be honest, low molecular weight (LMW) HA is a controversial ingredient. On the up side, it can penetrate the skin better and might be able to moisturize the deeper layers of the skin where normal HA just cannot get. On the downside, there is some research showing that LMW-HA acts as a pro-inflammatory signaling agent and might not be such a good idea to smear it all over ourselves. You can read much more about this controversy in the geeky details section of hyaluronic acid.