Electrolysis is actually a term for a chemical reaction which is utilized by one of the methods for electro-epilation. It is easier to say though so the name electrolysis stayed as most popular name for electro-epilation. Thermolysis is the other main method for electro-epilation. This one uses heat to destroy the follicular tissue and prevent further hair growth. It is very popular nowadays and many practitioners would do just thermolysis. As long as they are treating sufficiently to release the hair without traction and not over-treating the skin, you are in the right hands and the hair follicles are being killed first time.
Thermolysis is quicker method taking just a few seconds per hair, while classic electrolysis (galvanic electro-epilation) takes a few minutes per hair. Hardly anyone uses the latter anymore, but there is the method Blend that “blends” thermolysis and electrolysis capitalising on the speed of thermolysis and effectiveness of electrolysis. It is good to have it as an option for some clients whose hair/skin may be tricky to do with thermolysis.
How many times you would need the area cleared depends on quite a few factors, but if you have been plucking continuously for years and you didn’t wait at least 6 months from last plucking session to first electro session, you are likely to need a number of treatments. That’s NOT because the follicles may be distorted, but because plucking often messes the hair cycles of the area growth and instead of 3 cycles of, say, 1 000 hair follicles each, you have 30 cycles of 100 hairs each.
I hope this helps.