what is this in typescript <T> code example

Example 1: typescript generic class

class Person<T, U, C> {
  name: T
  age: U
  hobby: C[]

  constructor(name: T, age: U, hobby: C[]) {
    this.name = name
    this.age = age
    this.hobby = hobby
  }
}

const output = new Person<string, number, string>('john doe', 23, ['swimming', 'traveling', 'badminton'])
console.log(output)

Example 2: typescript class type t

class GenericNumber<T> {
    zeroValue: T;
    add: (x: T, y: T) => T;
}

let myGenericNumber = new GenericNumber<number>();
myGenericNumber.zeroValue = 0;
myGenericNumber.add = function(x, y) { return x + y; };