Filter sterilization and penetration battery

Currently sterilising filtration is one of the most commonly used techniques in the Pharmaceutical Industry. Some doubts and misunderstandings can, however, arise from certain aspects of this consolidated and well-known technology. Some examples? Does speaking about 0,2 or 0,22 um necessarily mean a sterilising filter? What are 0,1 um filters? How well do we understand the phenomenon of bacterial penetration in sterilising filters?