Order by SMS refers to the process of placing a purchase or request through a text message on a mobile phone. This convenient method allows customers to quickly and easily order products or services from a business without the need for a phone call or online transaction. With just a few taps on their phone, customers can send a text message containing their desired order and receive a confirmation or further instructions in return. This method of ordering is becoming increasingly popular due to its simplicity and accessibility, making it a convenient option for busy individuals on the go.