Are thos line necessary

Question

Thos lines should be in the code ?
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace SoloLearn
{
class Program
{
And what } do ?? Thank you

Answer 1

These are libraries which needed to be included in the program.
Not all I guess, but the first, third and fourth line is mandatory for almost all the C# programs.