Trello is a collaboration tool that organizes projects into boards. Boards contain lists where tasks are added as cards, allowing users to see who is working on what and where things are in the process. It helps users and teams stay organized, track progress, and have fun completing projects together. Users can customize cards by adding descriptions, checklists, attachments, due dates, and more to facilitate collaboration. The app also features power-ups like voting, card aging, and calendar integrations.