Make to Stock (MTS) is a build-ahead production approach in which production plans may be based upon sales forecasts and/or historical demand. 
Build to Stock (BTS) is a usually associated with the industrial revolution mass production techniques, where in anticipation of demand vast quantities of goods are produced and stocked in warehouses.

 BTS is frequently considered as an appropriate solution for high volume products where the demand is either seasonal or easily predicted, or both.

Some firms build all their products to order while others build them to stock. Given the widespread proliferation of products, there are a number of manufacturers taking a hybrid approach, where some items are built to stock and others are built to order.