Ready-to-wear has the same meaning as Prêt-à-Porter.
Ready-to-wear or prêt-à-porter is the term for factory-made clothing, sold in finished condition, in standardized sizes. In other words, you can walk into the store, buy the clothing, and it is ready to wear. You do not need to take special measurements or have tailoring done to the clothes. However, you obviously should try the clothing on in the fitting room to make sure that the clothing fits. Just because it is ready to wear, it does not mean that it is ready to fit you perfectly.
The fashion industry tries to utilize some standards, but to be honest, most manufacturers use different size specs. An exact uniformity of measurement does NOT currently exist in the fashion industry.
You also may have interest in learning about made-to-measure clothing.
Are you searching for the perfect pair of denim jeans to add to your trendy wardrobe?