A constant in math is like your favorite candy that never changes. You know that you always love that candy and it doesn't matter what else is going on, your love for that candy stays the same.
In math, a constant is a number that never changes. For example, the number 5 is a constant because it always means the exact same thing. No matter what math problem you use it in, it will always be 5.
Just like how you can't change your mind about your favorite candy and suddenly start loving broccoli instead, you can't change a constant in math. It will always be the same number no matter what.
Knowing constants in math is important because they help us solve problems and figure things out. They are reliable and always stay the same, kind of like how your favorite candy always tastes the same.