what is pvaValue.PriceAdjustment?

could anyone please explain what exactly  does "attributesTotalPrice += pvaValue.PriceAdjustment;" do in the following code?
its a method in the Catalog.PriceCalculationService

I am particularly interested in what pva.PriceAdjustment is and how its functioning

Thanks In advance!





/// <summary>
        /// Gets the shopping cart unit price (one item)
        /// </summary>
        /// <param name="shoppingCartItem">The shopping cart item</param>
        /// <param name="includeDiscounts">A value indicating whether include discounts or not for price computation</param>
        /// <returns>Shopping cart unit price (one item)</returns>
        public virtual decimal GetUnitPrice(ShoppingCartItem shoppingCartItem, bool includeDiscounts)
        {
            var customer = shoppingCartItem.Customer;
            decimal finalPrice = decimal.Zero;
            var productVariant = shoppingCartItem.ProductVariant;
            if (productVariant != null)
            {
                decimal attributesTotalPrice = decimal.Zero;

                var pvaValues = _productAttributeParser.ParseProductVariantAttributeValues(shoppingCartItem.AttributesXml);
                if (pvaValues != null)
                {
                    foreach (var pvaValue in pvaValues)
                    {
                        attributesTotalPrice += pvaValue.PriceAdjustment;
                    }
                }

                if (productVariant.CustomerEntersPrice)
                {
                    finalPrice = shoppingCartItem.CustomerEnteredPrice;
                }
                else
                {
                    finalPrice = GetFinalPrice(productVariant,
                        customer,
                        attributesTotalPrice,
                        includeDiscounts,
                        shoppingCartItem.Quantity);
                }
            }

            if (_shoppingCartSettings.RoundPricesDuringCalculation)
                finalPrice = Math.Round(finalPrice, 2);

            return finalPrice;
        }

It means that Value will affect the price of the product.

If I have a t-shirt that is $5 and the attribute is Size, I could set the values for Small and Medium to have a price adjustment of 0 but Large adds $1 to the price of the shirt.