What is wrapper class in Salesforce?

Hello Aman,

Wrapper we can understand as the outer part of any kind of things (object like custom, standard, checkbox etc)that is wrapped with some kind of material.

A wrapper is a class or container whose instance is a collection of other objects.

The best example is when you apply for any jobs in websites the page looks like checkbox, job description, apply button, there are different objects but all of them displayed in a single page that is wrapper class

example..
public class MyClassContainer{ //main class
public List<wrapClass> new List<wrapClass>(); //instance of wrapper class
public class wrapClass{ //wrapper class
List<Account> acct{get;set;}
List<Opportunity> oppt{get;set;}
List<contact> cnct{get;set;}
public wrapClass(Account acct , Contact cnct , Opportunity oppt){
acct = new List<Account>();
oppt = new List<Opportunity>();
cnct = new List<contact>();
this.acct = acct;
this.cnct = cnct;
this.oppt = oppt;
}
}
}

Here my class "MyClassContainer" contain three different collection object which is (List of Account, contact and Opportunity).

if we want to display three object which is Account, contact and Opportunity on one page then we make the instance of "MyClassContainer"
here the wrapper class comes into the picture.