Entity Framework configuration

this is my dbcontext

    public partial class TestModel : DbContext
    {
        public TestModel()
            : base("name=TestModel")
        {
        }

        public virtual DbSet<Department> Departments { get; set; }
        public virtual DbSet<Employee> Employees { get; set; }

        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            modelBuilder.Entity<Department>()
                .Property(e => e.DepartmentName)
                .IsUnicode(false);

            modelBuilder.Entity<Department>()
                .HasMany(e => e.Employees)
                .WithOptional(e => e.Department)
                .HasForeignKey(e => e.DeptID);

            modelBuilder.Entity<Employee>()
                .Property(e => e.Name)
                .IsUnicode(false);
        }
    }

Department and Employee has one-to-many relationship.

1) see this code

            modelBuilder.Entity<Department>()
                .Property(e => e.DepartmentName)
                .IsUnicode(false);

a) what is the meaning of this line .Property(e => e.DepartmentName) and this line .IsUnicode(false);

2) see this code

            modelBuilder.Entity<Department>()
                .HasMany(e => e.Employees)
                .WithOptional(e => e.Department)
                .HasForeignKey(e => e.DeptID);

a) what hasmany does .HasMany(e => e.Employees)

b) what withoptional does

c) department has no FK then why EF code generator use this .HasForeignKey(e => e.DeptID); ? actually employees table has FK.

please discuss about the above points in details.

thanks