In the description under a teaser, a trailer or an announcement, we often see a line such as Pre-save & Pre-add & Pre-order, set right next to a release date and followed by a link. The words look alike, and because they sit in a row they read as one thing, yet they name different actions. Each is a way to line something up before the release arrives, and that shared idea is where the confusion starts.
Pre-save and Pre-add are both about the digital release on a streaming service. When you use the link, it connects your own account to the release and queues it, so that it is added to your library when it comes out. We treat the two words as near-synonyms, since different services and link pages prefer one or the other. The exact wording varies, and a link normally asks you to sign in to a streaming account you already use. It is a connection, not a payment.
Pre-order is a different kind of action. It is a purchase made before release, usually of a physical edition such as an album, though sometimes of a digital one. Unlike a pre-save, it is a transaction, and the item is delivered or made available later. The description usually links a store or lists the stores. When we see that word, we read it as a checkout, not as an account connection.
What the three have in common is timing. Each one is tied to the release date given in the same description, and the action happens before that date. What differs is what you hand over: a pre-save asks for a connection between your account and the release, while a pre-order asks for payment. Read which word you are looking at before you click, because a link under one word can lead somewhere different from what the other word would suggest. If you choose to use a link, use the one in the official description, since the official post is where the real link sits, and take a moment over any page that asks for more than a streaming sign-in or a normal store checkout.