UI functions make it easy to add Trello-y user experiences to your Power-Up. For instance, if you need to let a user know that your Power-Up is doing something in the background, you might make use of t.alert() to send them a delightful message:

When rendering your own content inside of a UI function, we recommend sticking to the Trello Style so that there is a seamless transition between Trello and your Power-Up experience.