The term "onSubmit" refers to an event handler commonly used in web development, particularly in forms. It is triggered when a user submits a form, allowing developers to execute specific actions, such as validating input data or sending the information to a server. This functionality is essential for ensuring that the data collected is accurate and properly processed. In many programming languages and frameworks, such as JavaScript and React, the "onSubmit" event can be easily implemented. Developers can define a function that runs when the form is submitted, enabling them to manage user interactions effectively and enhance the overall user experience.