Probiotics are good bacteria that have been characterised for their beneficial properties. They work by rapidly reproducing and crowding out any bad bacteria. You might be familiar with probiotics aimed to maintain a good balance in the gut, but your gut is not the only place that has a microbiome worth keeping in balance.
Advanced probiotics are slightly different in that they also provide the benefit of producing bacteriocins (small proteins) that are inhibitory against other bacteria species. So, not only do they crowd out the bad bacteria, they inhibit them with bacteriocins.
However, not all probiotic strains can do this. BLIS K12 and BLIS M18 are both advanced probiotics strains that utilise Streptococcus salivarius, which means that they have this additional capability.