A spin bike is a stationary exercise bike designed for indoor cycling workouts. It features a heavy flywheel that provides resistance, allowing users to simulate outdoor cycling. Spin bikes often come with adjustable seats and handlebars to accommodate different body types and preferences. These bikes are commonly used in group fitness classes, where an instructor leads participants through various cycling routines. Spin bikes can also be used for individual workouts at home, making them a popular choice for those looking to improve cardiovascular fitness and build leg strength.