Your account has more storage for your media, and also unmetered bandwidth.
Your account and your links to third-party websites remain active for the duration of your PLUS subscription.
If you had a free account (or PRO account) on the previous version of Photobucket, you will get the additional GB on top of what you've already stored. For example, if you had 1 GB of images on the original Photobucket, on the new Photobucket you will have 2 GB + 1 GB = 3 GB of total storage available on the new photobucket.
If you're already a Plus subscriber but require more storage, or wish to upgrade from your free account and don't know the way, please visit this link: Get more storage!