A need is something required to live safely and healthily: food, shelter, clothes, and basics like soap or school supplies.
A want is something nice but optional: extra toys, candy, the newest video game, or designer sneakers when regular shoes work fine.
When it is not obvious
Some things are both. You need shoes, but you might want the expensive pair. You need lunch, but you might want takeout instead of packing a sandwich.
Ask: What happens if I skip this? If the answer is I would be cold, hungry, or unsafe, it is closer to a need. If the answer is I would just be bored, it is probably a want.
Why this helps you save
Money is limited. If you spend on wants first, you might not have enough for needs or goals.
Needs vs. wants is not about never having fun. It is about choosing wants on purpose after needs and savings are covered.
Practice
Before your next purchase, label it need or want. If it is a want, check your spend jar. Use the savings goal calculator to see how waiting a few weeks could help you afford something bigger.