At the risk of sounding obtuse, I will say management is defined as those people who are bosses of companies. To drill down, management can refer to groups of people given the responsibility of looking after a division or project within a business. They may or may not be assigned a team of people to look after. They also may or may not have a budget to work with.
For example…
The management team at Sky High energy drinks, husband and wife, Shaun and Lisa have a couple of other people overseeing their overseas markets in New Zealand and Singapore. So, for those people employed in those countries, the team leaders monitoring operations are their immediate management team, however, Shaun and Lisa are the highest level of management for Sky High.