Before you can disinfect, you have to clean. To clean something is to remove contaminants such as dirt, dust, grease, soot, grime (dirt ingrained on the surface of something) and residue (sticky film or gooey stuff left behind). Cleaning is important because if a surface is not clean, pathogens have more places to cling to. Cleaning will usually remove most bacteria and other microbes.
Sanitizing is what you do before disinfecting. Sanitizing is removing microorganisms to a safe level. The safe level is defined as removing 99.9% (3Log10) of bacteria (but not viruses and fungus). The key word here is most. When you sanitize a surface, you are removing enough bacteria to consider the surface safe. Food establishments typically follow sanitization protocols where the surface is safe for food preparation after the sanitization solution has dried off the surface.
Disinfection kills almost all bacteria, viruses, and fungus on a hard non porous surface to safe levels. Disinfectants do not kill 100% of all micro-organisms on a surface, but they get 99.9999% close (the fancy math term for this is 6Log10). To achieve 100% removal of all microorganisms is called sterilization. Disinfectants by nature are toxic to humans and should only be used when there is a high risk of exposure ore re-exposure to viruses. Some examples include, locker rooms, hospitals, care homes, and other institutions frequented by many people. Disinfectants should only be handled while wearing proper personal protective equipment (PPE). Disinfection can take place by physical means, such as using light or heat, or by chemical means.