What is the difference on using abstract class to override method and normal class to overrride method in java or any programming languages?

Overriding Abstract Classes in Java

In Java, it is compulsory to override abstract methods of the parent class in its child class because the derived class extends the abstract methods of the base class.

If we do not override the abstract methods in the subclasses then there will be a compilation error.

package com.techvidvan.abstractclass;
abstract class Parent
{
  //concrete method
  public void display1()
  {
    System.out.println("Concrete method of parent class");
  }
  //abstract method
  abstract public void display2();
}
class Child extends Parent
{
  // Must Override this method while extending Parent class
  public void display2()
  {
    System.out.println("Overriding abstract method");
  }

  //Overriding concrete method is not compulsory
  public void display1()
  {
    System.out.println("Overriding concrete method");
  }
}
public class AbstractClassDemo
{
  public static void main(String[] args)
  {
    Child obj = new Child();
    obj.display2();
    obj.display1();
  }
}

more on:

link