Cold atmospheric plasma (CAP) treatment of living tissues becomes a popular topic in modern plasma physics and in medical sciences. The plasma is capable of bacterial inactivation and noninflammatory tissue modification, which makes it an attractive tool for wound healing and the treatment of skin diseases and dental caries. There are still many open issues with regard to the mechanisms of action of the plasma on bacteria and mammalian cells and tissues, both from the biological and the physical perspective. For example, the chemistry of CAP and the exact roles of various plasma constituents in tissue treatment are not yet fully resolved. In this paper, we shall concentrate on the charged species (electrons and ions) in the plasma. The selected physical properties of typical atmospheric plasma sources will be discussed; experiments will be confronted with theoretical considerations, and several biomedical aspects of CAP treatment will be surveyed.