Un Fragment es una porción de interfaz de usuario reutilizable que vive dentro de una Activity — un componente de interfaz modular y autónomo con su propio ciclo de vida. Los Fragments permiten interfaces de usuario flexibles y reutilizables y son centrales en arquitecturas modernas de una única Activity.
Qué es un Fragment
A FRAGMENT = a reusable, modular piece of UI hosted inside an Activity:
→ has its OWN lifecycle (tied to but distinct from the host activity's)
→ multiple fragments can be combined in one activity; reused across activities
→ represents a portion of the screen (or a whole screen's content)
→ Think: an activity can host one or more fragments that make up its UI.
