Items on the roadmap are like groceries on your shopping list. They become effective only when really being worked on by teams which happens by turning them into items on the product backlog. As the nature of the backlog heavily depends on the delivery framework in use, we will only briefly touch on product backlogs here.
Nothing gets done by the team that isn’t on the product backlog. Conversely, just because an item is on the backlog does not guarantee it will be done — the selection of the items to be worked on is up for joint refinement and planning as part of the delivery process.
A product backlog is a list of the new features, changes to existing features, bug fixes, infrastructure changes or other activities that a team may deliver in order to achieve a specific outcome.