While Leads are used in a couple of other recipes, specifically for Balloons, their primary use is leashing mobs. You can leash just about every creature in Minecraft, but you'll find the most use for ...

A string is a primary item dropped from spiders, cave spiders, striders, and cats. Spiders, cave spiders, and cats drop 0-2 strings on death, while the striders can drop up to 5 strings. With Looting ...