A user interface (UI) is the space where interactions between humans and machines occur. It encompasses all the elements that allow users to communicate and engage with software applications. The UI can include buttons, icons, menus, and any visual aspects that facilitate user experience. A well-designed user interface aims to make the user's interaction as efficient and intuitive as possible, ensuring ease of use and accessibility while fulfilling functional requirements. Ultimately, the objective of a UI is to enhance user satisfaction by providing clear pathways for interaction.