You can cut your own at home, or buy them precut. Sometimes they are cut quite chunky, for “chicken fingers”; other times, they are cut more finely for stir fries, etc.
Though not an official term that is enforced anywhere, Chicken Breast Strip seems to always apply to white breast meat. However, it doesn’t always apply to just plain, raw pieces of meat: it can also be applied to precooked, breaded and spiced Chicken Breast Strips.
The United States Department of Agriculture (USDA) in 1995 defined Chicken Tenders as basically being Chicken Breast Strips.
You can make your own Chicken Breast Strips from chicken cutlets, fillets or whole chicken breasts that you have bought.