Downloading app on iMac asks for Administrator Details.

Applications that require components installed outside of your home directory will prompt you with an administrator password request. Unless you chose an Apple ID password identical to your administrator password (not a good idea), then you provide the administrator password in order to enable the installation to proceed.

If that app is not directly from the original developer website, then you should think twice about installing it with the elevated privileges associated with the adminstrator.

kiddehoglund wrote:

administer - is this the same as Apple-ID? The reason I ask is that when I try to download a new program it says give the name of administer.

Thank you

No

Normally the " Owner Account  " is the very first Account used when the Computer was Very First Setup as New and out of the box.

The " Owner Account of this computer "  has that privilege to add, remove, upgrade or downgrade accounts.

Set up users, guests, and groups on Mac

Adding additional Admin Account can be done by the Original Admin Account holder