How do static electricity and electric discharge differ?
Static electricity are charges accumulated on bodies of substances. In electrostatics, we study forces, fields and potentials associated with such charges. These are not in motion. Static charges only create steady electric fields.
Electric discharge takes place (we are considering the case of a CRT) when a sufficiently high voltage is applied across the plates enclosing an evacuated gas (very low pressure), the high electric field ionizes the gas molecules by pulling the electrons apart.
This the the case of electric discharge and we are able to find cathode rays (due to electrons) and canal rays (due to positively charged gaseous ions).