https://developer.mozilla.org/en-US/docs/Learn/Forms/How_to_structure_a_web_form
The form element usually defines a form and attributes that determine the forms behavior.
The fieldset element is an convenient way to make groups of widgets that all share the same purpose.
The (label) element is the formal way to define a label for an HTML form widget. This is the most important element if you want to build accessible forms — when implemented properly, screen readers will speak a form element’s label along with any related instructions, as well as it being useful for sighted users.
Forms are one of the main points of interaction between a suer and a website. These web forms allow the user to enter data.
A web form’s HTML is made up of one or more form controls (sometimes called widgets), plus some additional elements to help structure the overall form — they are often referred to as HTML forms. The controls can be single or multi-line text fields, dropdown boxes, buttons, checkboxes, or radio buttons, and are mostly created using the input element.
Events are things that happen in the system you are programming — the system produces (or “fires”) a signal of some kind when an event occurs, and provides a mechanism by which an action can be automatically taken (that is, some code running) when the event occurs.