Vine, the weird looping video service powered by Twitter, is ending its service today. While the site will remain available as an archive, today's the last chance you'll have to download your videos easily.
From your desktop computer, head to the Settings section of the Vine web site, then click the "Request Your Archive" button. This will send you an email with a link to the ZIP file including all your Vine videos.
If you're on the mobile app, open the app, tap your profile, then tap the "Save Videos" button. From here, you can select which videos you want to download and they will be saved to your phone.
As for the Vine app, that's going to become Vine Camera, which will effectively be the camera part of Vine without the social network. Your videos will remain on Vine, but you won't be able to easily download them any more.