Hi Ellen, in Australia, the name 'Daddy long-legs' is used to refer to a specific spider, Pholcus phalangioides
and the members of the order Opiliones (Harvestmen). Harvestmen are related to spiders and belong in the same Class Arachnida, but differ from spiders by not having an obvious division between the cephalothorax and abdomen. You can find more information and links on our Question of the week
about these Arachnids.