In React Native , Two types of components can be created.One is Functional Component and Class Component is another.

Function Component:

Function components are static components.
It simply returns children.
It does not have any states.
It is a simple one to create and use.

Class Component:

Class components are dynamic components.
The state of class components can be changed.
Class components have lifecycle methods.

Component Lifecycle:

ComponentWillMount
ComponentDidMount
ComponentUnmount

ComponentWillMount:

WillMount is a state which occurs as a preloader of a page ComponentDidMount
DidMount state occurs after the page load is complete ComponentUnmount
Unmount state is a final state of a component.
Unmount state, Occurs when component move from one to another