What is a low medium and high-frequency?

Low-frequency sounds are 500 Hz or lower while high-frequency waves are above 2000 Hz . Human ears can register sounds from about 20 Hz in frequency up to 20,000 Hz, depending of course, upon the hearer.

At sufficiently high frequencies, most of the current will flow close to the surface of the conductor (being the human body). So there could be thermal effects (burns on the skin) but the most vital organs inside will get much less of a hit . , electronics/electrical engineering.

an alternating electric current having a frequency of 10,000 or more cycles per second ; it produces no muscular contractions and does not affect the sensory nerves.