Address Validation provides information to determine whether a given address exists and can be used for account sign-up, checkout, or delivery. By comparison, Autocomplete is a type ahead solution that helps with speeding up address entry, but in prioritizing the user’s entry experience doesn’t guarantee validity of the addresses. Address Validation can be used afterwards to catch incorrect or missing components, like subpremises (e.g. apt #), to improve the delivery experience.
While Geocoding converts addresses to geographic coordinates or the reverse, Address Validation provides confirmation level per component, allowing you to provide feedback to your users on how to correct an invalid address.
Geocoding API focuses on identifying a real-world location based on a given input, but in doing so may identify a location that is different than the input address or omit certain parts of the input address. Address Validation focuses on the input address and providing feedback on all parts of it, including confirmation level per component.