Someone or something that's ill-equipped isn't suited or prepared to do a certain task. If you faint at the sight of blood, you're probably ill-equipped to be a surgeon.
Soldiers without weapons or armor are ill-equipped for battle, and if you don't have an umbrella or a raincoat, you're ill-equipped for walking to school in the pouring rain. You might also be emotionally or temperamentally ill-equipped. If you are afraid of heights, you are most likely ill-equipped to be a roofer. When someone's equipped, they have the proper equipment, and when you add the prefix ill-, it's clear they're lacking what they need.