Component

A reusable, self-contained piece of UI code, like a button, card, or navigation bar. Components can be combined to build complex interfaces without duplicating code.

Thinking in components means your UI is consistent (the same button looks the same everywhere), faster to build (build once, use anywhere), and easier to update.

A founder's app has a "PricingCard" component used on three different pages. When she updates the price, she changes one file, all three pages update instantly.