Almonds are not true nuts; they are the seeds of the fruit produced by the almond tree.
Why it is true
Botanically, almonds are drupes, related to peaches and cherries. The part we eat is the seed inside the hard shell of the fruit.
Source: Botany
Would you rather be asked first?
This is the reading side of the site, so the answer is in the sentence above — that is the whole point of it. Test yourself works the other way round: the question comes on its own, and the fact and the explanation only appear once you have answered.