You want to describe a student once: every student has a name and a year. Then, everywhere a student is used, TypeScript checks that it really has both.

Think of an admission form. It lists the fields: name, in letters; year, as a number. Every filled form must have those fields. An object type is that blank form. Each real student object is one filled form.

type Student = {
  name: string;
  year: number;
};
const rafi: Student = { name: "Rafi", year: 2 };

type Student = ... gives the shape a name. This is called a type alias. Inside, each line is a property and its type. They end with ;, not ,, because this is a description, not a real object. rafi: Student means "rafi is a Student", so it must have a name that is a string and a year that is a number.

You'll also see the same idea written with interface:

interface Student {
  name: string;
  year: number;
}

For reading code, type and interface mean the same thing: the shape an object must have. Teams just pick one style. Once the shape has a name, you use it like any type: Student[] is an array of students, and function label(student: Student) takes one student.

If an object doesn't match, TypeScript tells you how:

• A field is missing: Property 'year' is missing in type '{ name: string; }' but required in type 'Student'.
• A field has the wrong type: year: "2" gives Type 'string' is not assignable to type 'number'.
• An extra field: age: 20 gives Object literal may only specify known properties, and 'age' does not exist in type 'Student'.

People often think type Student creates a student. It doesn't. It creates nothing when the app runs. It is only a description used for checking, and it is removed with the other types.

When you read a React Native file, look near the top for type ... = { or interface ... {. Read each line as "this object has a ___ that is a ___". That tells you what every object of that type holds.