What an information architect does and what information architecture (IA) is are two distinct things.
An information architect will oversee things like website navigation and user experience, while IA (the term) relates to the system and structure of websites and applications. Information architects will also work with other departments to ensure information is presented to users clearly.
In many cases, organizations won’t actually have a dedicated information architect. Instead, the duties and tasks typically associated with the role will be carried out by designers, content strategists, developers and product managers.