what does "wheel" mean for custom access

wheel= admin

In computing, the term wheel refers to a user account with a wheel bit, a system setting that provides additional special system privileges that empower a user to execute restricted commands that ordinary user accounts cannot access. The term is derived from the slang term big wheel, referring to a person with great power or influence. It was first used in this context with regard to the TENEX operating system, later distributed under the name TOPS-20 in the 1960s and early 1970s.

The term was adopted by Unix users in the 1980s, due to the movement of operating system developers and users from TENEX/TOPS-20 to Unix. Modern Unix implementations generally include a security protocol that requires a user be a member of the wheel user privileges group in order to gain superuser access to a machine by using the su command.

The wheel group is a group which limits the number of people who are able to su to root. This usually consists of a group named “wheel” and a set of users that are permitted to use the utility ‘su’ in order to change to root.

Normally in OS X the only member of the wheel group is "root", the system superuser. The membership of the admin group includes the admin user accounts as well as root.