public class Employee
 {
      public int Id { get; set; }
      public string Name { get; set; }
 }

IList<Employee> EmpList ;

Or

List<Employee> EmpList ;

IList<Employee> EmpList = new List<Employee>();

List<Employee> EmpList = new List<Employee>();

var EmpList = new List<Employee>(); // EmpList is List<Employee>

IList<Employee> EmpList = new IList<Employee>();

public void IterateEmployees(IEnumerable<Employee> employees)
{
   foreach(var employee in employees)
   {
     // ...
   }
}

//this will not compile
IList<Employee> EmpList = new IList<Employee>();

//this is what you're really looking for:
List<Employee> EmpList = new List<Employee>();

//but this will also compile:
IList<Employee> EmpList = new List<Employee>();

[SerializableAttribute]
public class List<T> : IList<T>, ICollection<T>,
    IList, ICollection, IReadOnlyList<T>, IReadOnlyCollection<T>, IEnumerable<T>,
    IEnumerable