How delegate work

Filter.cs

delegate bool SomePredicate<T>(T a);

public List<T> Filter<T>(T[] input, SomePredicate<T> function)
{
    var newList = new List<T>();
    foreach(var element in input)
    {
        if (function(element))
        {
            newList.Add(element);
        }   
    }
    return newList;
}