Как работает group by? - C#

namespace consoleApp
{
    public class Program
    {
        static void Main(string[] args)
        {
            var participants = GetAll().ToList();
            var result = participants.GroupBy(p => p.Gender).Select(g => new { Gender = g.Key, Participants = g.OrderBy(p => p.Time).Take(3) });
            foreach (var group in result)
            {
                Console.WriteLine(group.Gender);
                foreach (var participant in group.Participants)
                {
                    Console.WriteLine(participant.ToString());
                    Console.ReadLine();
                }
            }
        }
 
        public static Participant[] GetAll()
        {
            return new Participant[]{
                new Participant("Alex", "g1", Sex.Male, TimeSpan.FromSeconds(67)),
                new Participant("Mark", "g2", Sex.Male, TimeSpan.FromSeconds(98)),
                new Participant("Ann", "g3", Sex.Female, TimeSpan.FromSeconds(123)),
                new Participant("Kate", "g2", Sex.Female, TimeSpan.FromSeconds(75)),
                new Participant("Peter", "g3", Sex.Male, TimeSpan.FromSeconds(69)),
            };
        }
    }
 
    public struct Participant
    {
        public string Surname;
        public string Group;
        public Sex Gender;
        public TimeSpan Time;
 
        public Participant(string surname, string group, Sex gender, TimeSpan time)
        {
            Surname = surname;
            Group = group;
            Gender = gender;
            Time = time;
        }
 
        public override string ToString()
        {
            return $"{Surname} {Group} {Gender} {Time}";
        }
    }
 
    public enum Sex { Male = 1, Female = 2 };
}