These options are used to hide the price when signing a member to a specific membership level. 

This feature is helpful for cases where the partner only wants to offer a specific price for a particular membership plan on the pricing page, but would also want to have the ability to upgrade specific members in the case they do not want to maintain a monthly, yearly or even semi-yearly payment.

The admin for this cases will be able to upgrade the member's account to another payment option through a request by the member (email, telephone call, etc..). So the result would be that the signed members would see a list of payment options, but they could be offer additional ones (The ones marked as Admin Only) if they requested this to the partner or wanted to change to a special type of payment option for their membership plan.

How it works? 

For example, we have a membership level called "Featured". In our membership level, the pricing is shown in the image below where you can see two prices. A monthly price of $9.99 and a yearly price of $99.99, none of which are set as Admin Only:

If you try to sign up using this membership level, you would see on the sign up page the following:

If you mark the option "Admin Only" in the Yearly Price as seen in the following image, this option will disappear from the payment page:

We have marked the Yearly Price as "Admin Only", this would result in the sign up process showing like this:

As you can see, only the Monthly Price is shown, the yearly price has disappeared from the list. 

Now if we go ahead and mark both options as "Admin Only":

Our end result on the sign up page would be this: