A "Virtual Team" is used to describe a team that doesn't really exist within your organisation's structure.
Consider a Virtual Team as a way to group users from different teams, such as a cross departmental project, or a team that is spread out geographically.
Virtual Teams can be assigned an approval workflow in exactly the same way as a normal team.
Depending on how the Domain Administrator configures this approval process, a user's Virtual Team manager can be alerted as well as their normal team manager when they make a holiday request.
Administrators can decide where a user's virtual team approval should fit into their existing approval workflow. This way Administrators can design an approval workflow that takes into account both a user's line manager and project manager in the order that best fits your organisation.
Please note that additional steps are required if you want users to have virtual team approvers. Please refer to this learn article on how to add a virtual team approval flow to your team profile.
See this learn article on how to add employees to your new Virtual Team.