why we need to mongoose schema code example

Example 1: mongoose schema

/// model/User.js 

const mongoose = require("mongoose");

const UserScheme = mongoose.Schema({
  name: {
    type: String,
    required: true,
  },
  email: {
    type: String,
    required: true,
    unique: true,
  },
  password: {
    type: String,
    required: true,
  },
  date: {
    type: Date,
    default: Date.now(),
  },
});

module.exports = mongoose.model("user", UserScheme);

Example 2: mongoose schema

const mongoose = require('mongoose');

const UserSchema = new mongoose.Schema({
    name: {
        type: String,
        required: true
    }
}, {
    timestamps: true
})

const User = mongoose.model('User', UserSchema);

module.exports = User;

Example 3: mongoose schema

var mongoose = require('mongoose');
  var Schema = mongoose.Schema;

  var blogSchema = new Schema({
    title:  String, // String is shorthand for {type: String}
    author: String,
    body:   String,
    comments: [{ body: String, date: Date }],
    date: { type: Date, default: Date.now },
    hidden: Boolean,
    meta: {
      votes: Number,
      favs:  Number
    }
  });