Why we use require() Function in SuiteScript2.0 in Netsuite?

The require() function is used to load modules. When you use the require() function, dependencies are not loaded until they are needed.
The record module is loaded when record.create() is called.
The require() function does not return a value.

/**
 *@NApiVersion 2.x
 */
require(['N/record'],
    function(record)
    {
        function createNewContact() 
        {
            var nameData = {
                firstname: 'Abhi',
                middlename: 'K',
                lastname: 'P'
            };
            var recordObj = record.create({
                type: record.Type.CONTACT,
                isDynamic: true
            });
            recordObj.setValue({
                fieldId: 'subsidiary',
                value: '1'
            });
           
            var recordId = recordObj.save({
                enableSourcing: false,
                ignoreMandatoryFields: false
            });
        }
 
        createNewContact();
    });

 //this script is just example , change your logic as per your need.