A vacancy usually exists once a role has been approved and funded but nobody is in post. It may be a new position or a replacement for someone who left or moved internally. Most organisations track vacancies through a job requisition, which records the role, location, budget and hiring manager, and gives the vacancy a reference that follows it through to hire.
Every open vacancy carries a cost, from lost output to overtime and strain on colleagues, which is why vacancy numbers and age are watched closely in workforce planning. Before advertising, it is worth confirming what the role really needs rather than copying the last job description. Clear must-have criteria agreed at the start make screening faster and keep assessment consistent.