Does anybody know what knot am I talking about?

[Voltimolt]

theres 2 knot, the farer they go, the shorter the rope and closer they are the more long they are.

i dont know if anyone understands this but i really need to know for my necklace. my necklace used to do that but i got them too close the knot just messed up. and it looks ugly.

if you can really help me, please tell me ;(