On-demand service refers to a business model that allows customers to access products or services whenever they need them, rather than following a fixed schedule. This model is commonly seen in industries like transportation, where services such as Uber and Lyft enable users to request rides instantly through a mobile app. In addition to transportation, on-demand services are prevalent in areas like food delivery, with platforms like DoorDash and Uber Eats allowing users to order meals from local restaurants at their convenience. This flexibility caters to the fast-paced lifestyle of modern consumers, making it easier to meet their immediate needs.