Ienumerable interface in C#

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C#

Hello guys, was just learning about IEnumerable interface and found that we can iterate through generic as well as non-generic collection with the help of IEnumerable interface, but then just to check i created a class Customer with some attributes.Then in Main method created a array of that Class adding few objects.Then ran through foreach loop and worked fine without using IEnumerable Interface.Can u explain, may be my question would be weird or foolish, but to be onest not able to understand exactly what is IEnumerable and when and why to use IEnumerable interface.Thanks in advance if anyone can explain in Detail.

public class Customer1
    {
        private String _Name, _City;
        private long _Mobile;
        private double _Amount;

        public String Name
        {
            get { return _Name; }
            set { _Name = value; }
        }
        public String City
        {
            get { return _City; }
            set { _City = value; }
        }

        public long Mobile
        {
            get { return _Mobile; }
            set { _Mobile = value; }
        }
        
        public double Amount
        {
            get { return _Amount; }
            set { _Amount = value; }
        }
    }
    class IEnumerableTest
    {
        static void Main()
        {
            Customer1[] customers = new Customer1[]
            {
             new Customer1 {Name="Vithal Wadje",City="Mumbai",Mobile=99999999999,Amount=89.45 },
             new Customer1 { Name = "Sudhir Wadje", City = "Latur", Mobile = 8888888888888888888, Amount =426.00 },
             new Customer1 { Name = "Anil", City = "Delhi", Mobile = 7777777777777777777, Amount = 5896.20 }
            };

            foreach (var obj in customers)
            {
                Console.WriteLine(obj.Name + " " + obj.City + " " + obj.Mobile + " " + obj.Amount);
            }
        }
    }

What I have tried:

I have  created a class Customer with some attributes.Then in Main method created a array of that Class adding few objects.Then ran through foreach loop and worked fine without using IEnumerable Interface.