Body piercing - navel question

[justagnes]

I'm wanting to get a navel piercing and was going to book, but it gives options of internally threaded or externally threaded jewellery. Can anyone shed any light on this please?

amatopiercing.com/2019/02/13/internal-threading-vs-external-threading-dont-get-screwed-by-catchy-marketing-terms/

Get internally threaded jewellery, every time.

Thank you very much!