A groupset is the whole collection of parts that make up a gearing drivetrain and a braking system. Whether you're building up a new frame from scratch or your existing bike is a bit too worn ourt and beaten up, it makes a whole lot of sense to buy a complete groupset for your road bike rather than getting individual components
, such as a pair of brake levers
. As well as being much cheaper this way, you are also guaranteed to have fully functioning and fully compatible components.