Almonds are a familiar type of nut. They can be sweet or bitter, depending on the type of tree that produces them. Sweet almond is produced from one type of almond tree (Prunus amygdalus var. dulcis) and does not contain poisonous chemicals. Bitter almond comes from a different type of almond tree (Prunus amygdalus var. amara) and does contain toxic chemicals.
"Bitter almond" volatile oils can also be produced from other related fruit kernels including apricot (Prunus armeniaca), peach (Prunus persica), and plum (Prunus domestica).