A product roadmap is a sequence of items to work on ideally with only 1 larger item in-progress at a time.
Product roadmap is used to communicate sequence of work that team is doing to everyone involved (Stakeholders, E-Staff, business leaders, other teams). This provides visibility for stakeholders to ensure that team works on the "right" items and creates alignment within the team.
Communicate when specific items will be completed.
Highlight important milestones for product.
In a high performing teams product roadmap is owned by the product manager working on the product. It is necessary to have feedback loop between stakeholders and product manager to ensure alignment on the roadmap.