A checkbox is a small square that someone can mark or clear to choose an option. It works like ticking a box on a paper list: marked means “yes, include this,” and empty means “no.”
For example, a form might ask if you want email updates. Checking the box turns that choice on; leaving it empty keeps the choice off. In a list of checkboxes, people can often select several options at once.
Write a clear label next to each box so the person knows exactly what they are agreeing to. Do not preselect an optional choice when it is important that the person actively decides.