The deputy chief of staff is the most common of these roles and can be found in institutions that require support structures to assist the chief of staff in managing complex agendas.
In the US White House, the Deputy Chief of Staff is the formal top aide to the White House Chief of Staff, who is in turn the senior aide to the President. The office of Deputy Chief of Staff is located in the West Wing and their main duties include running the White House bureaucracy and completing special projects and other ad-hoc tasks set by the Chief of Staff.
In some administrations, multiple deputies have served concurrently. The Trump administration employed three deputy chiefs; Chris Liddell, Deputy Chief of Staff for Policy Coordination; Tony Ornato, Deputy Chief of Staff for Operations; and Dan Scavino, Deputy Chief of Staff for Communications.