There are several components and mixins available to help make working with forms easier.
Much like a native <form> element, <d2l-form> groups nested form elements together and controls how their data is validated and submitted. Unlike native <form>s, it supports our custom form elements.
See: Form Layout and Validation
To allow custom elements to participate in <d2l-form> submission and validation, use the FormElementMixin.
If your custom element uses other nested custom form elements internally, read about form element nesting.
On the other hand, if your custom element uses other nested native form elements internally, read about form element wrapping.