Pick an occasion, tap a card, edit the front text, add your personal message, choose how it opens, then Save & share. The card exports as a normal video you can send anywhere.
The share sheet offers Save Video (to your Photos), Messages, Mail, and any app that accepts videos. Nothing is uploaded — the video is made entirely on your device.
An option on the message page: your words are written out stroke by stroke, like a pen, in the finished video. You can pick from several pen styles.
Tips are processed by Apple as in-app purchases. They're a thank-you — they unlock nothing. For refunds of any purchase, use Apple's Report a Problem, which handles all App Store refunds.