UI components are the reusable building blocks of an interface — buttons, text fields, checkboxes, navigation bars, cards, and modals (pop-up windows) — each with conventions users already recognize from using other apps. Design patterns are proven solutions to recurring problems, such as using a hamburger icon (three horizontal lines) for a hidden navigation menu or a magnifying glass icon for search; reusing familiar patterns reduces the learning curve because users bring expectations from every other app they have used. Many teams collect their components and patterns into a design system — a shared library of reusable elements and rules — so that every screen looks and behaves consistently and designers don't have to redesign a button from scratch for every new feature.