求解答，c#中定义属性时，前面加的东西是什么意思

请问在定义属性的时候在上面加    [BelongsTo("DepartmentId")] 或者 [Property()]是什么意思，如下：
  [BelongsTo("DepartmentId")]
        public Department Department
        {
            get
            {
                return this._department;
            }
            set
            {
                this._department = value;
            }
        }


        [Property()]
        public decimal Price
        {
            get
            {
                return this._price;
            }
            set
            {
                this._price = value;
            }
        }