Heat capacity is like a superhero power that a material has, which makes it able to either tolerate or absorb a great deal of heat. It is a measure of how much heat is required to raise the temperature of something by a certain amount.
Imagine you have a big bucket of water and a smaller bucket of water, both at the same temperature. If you add the same amount of heat to both buckets, the smaller bucket of water will get hotter way faster than the big bucket. This happens because the smaller bucket of water has lower heat capacity.
Heat capacity is like the size of the bucket. The bigger the heat capacity, the more heat a material can "hold" before getting hot. On the other hand, if a material has low heat capacity, it heats up quickly.
For example, metal has a high heat capacity. That's why if you leave a metal spoon in a hot soup, it will get very hot, but it will take a while for it to become so hot that you can't touch it. Meanwhile, something with low heat capacity, like plastic, can become too hot to touch quite quickly.
Overall, the heat capacity of a material is important for things like making engines, electronics, or even cooking, because it determines how much heat is required to make something hot.