Lactobacillus Ferment Lysate Filtrate is a probiotic ingredient with soothing and maybe some anti-aging properties. It is produced by promoting Lactobacillus bulgaricus cells to secrete stress response elements. The secretion is then isolated and extracted from the live bacteria cell and voila, Lactobacillus Ferment Lysate Filtrate.
As for what it does in a cosmetic product, the manufacturer did several in-vitro (made in tubes) and one in-vivo (made on people) study. The in-vitro studies found plenty of good things: Lactobacillus Ferment Lysate Filtrate promoted oxygen uptake, collagen production, and ATP (the energy molecule in our body) synthesis in test tubes, however, these things might or might not happen when we smear it onto our faces. The only in-vivo, aka made on people study shows that our probiotic guy has some nice soothing and anti-irritant props. Though it was done only with 5 people, 5% of Lactobacillus Ferment Lysate Filtrate showed a 47% reduction in redness.