Autocomplete
A text input that suggests matches as the user types.
An autocomplete starts as a normal text field, but as soon as the user types, a list of suggestions drops down underneath. The list shrinks with each keystroke. Picking a suggestion fills the field.
Autocomplete shines when the answer comes from a long known set — a list of cities, products, or users. It saves typing and prevents typos. Match speed matters; suggestions that lag feel broken.