“if any product price changes while the order is not locked will automatically update the line items.”
To lock the pricing on an Order, click the ‘Lock Pricing’ button on the ribbon. Once the pricing has been locked, it can be unlocked again by clicking the ‘Use Current Pricing’ button. Similarly we can use the button on Invoice, Order and Quote etc.. when we use current pricing on an Order, the prices for all related line items will be updated to the current product pricing.
You can test this by adding the product to Order/Invoice/Quote and change the price of the same product and refresh the record, you will see the updated price for OrderProduct/InvoiceProduct/QuoteProduct.
Hope this helps.