How do you call that kind of hair extension where they melt something that seals the strands to the

i saw it on tv and the styler inserted a bunch of strands on a rubber/plastic tube and then inserts it to the real hair and applies heat (scissor-looking contraption) to melt the tube to seal it to the hair.

How do you call that kind of hair extension where they melt something that seals the strands to the hair?

It's called bonding. The extensions are glued to your own hair

How do you call that kind of hair extension where they melt something that seals the strands to the hair?

They are called shrinkies. You put the extension hair tip through it after you thread a small strand of your own hair in. The heat clamp shrinks the shrinkie on and it's how the hair extensions are applied.