Excerpt from "Kelvin @ SG" :

Are almond the nuts in the core of apricots?

Kelvin

Close but not quite. Apricot kernels are moderately toxic (cyanide?) but not
harmful in small quantities. Toxic principle in apricot kernels, referred to aslaetrile, is thought by some people to help treat or prevent cancer. Apricot
kernels are said to be bitter in taste, "bitter almonds", and there has been
the recommendation by apricot kernel proponents to eat two apricot kernels a
day to help prevent cancer. I haven't heard much recently about this use of
apricot kernels, maybe it didn't produce convincing results?

Almonds are closely related to apricots, but with almonds, the outer fruit
withers away, leaving a sweet edible kernel inside a shell whose hardness
varies according to variety. Common commercial variety is Peerless, and the
shells are easily cracked with a hand-held nutcracker.