It specifies a list of pre-defined options for an <input> element, It's used to provide an "autocomplete" feature for <input> elements. Users will see a drop-down list of pre-defined options as they input data.

Input suggestion/autocomplete box specifies the predefined options for an <input> element. it also gives the autocomplete feature for the <input> element of HTML. Like once the user starts typing in input field the user will see the pre-defined options starting with the letter or word typed by the user

Input suggestion/autocomplete box allow user to choose any option from the given list but can also use its own input.