What's the "Get it later" option for a hold?
When a hold is available, you'll get a notification with two options: Borrow and Get it later.

If you're not ready to borrow the book (for example, if you don't have time to read it), you can select Get it later. This pauses your hold and keeps you at the top of the wait list.
When you're ready to read the book, you'll need to resume the hold. You'll be notified when the next copy is available so you can borrow it.