I'm looking for a term for the line where the fingers emerge from (I highlighted this place with a yellow colour). What is this called?
Thanks to @Katy in the comment, I found the answer: palmar digital crease.
"Digital creases. Usually there are two creases at the level of each joint, being most prory, inent the proximal one. The palmar digital crease of the triphalangeal fingers is usually located at the proximal third of the proximal phalanx. The palmar digital crease of the thumb is longitudinally oriented and slightly proximal to the metacarpo-phalangeal joint." (skin creases)