2×12 means your bike has two chainrings up front and twelve gears on the cassette in the back, giving you 24 total gear combinations. It's the current standard on modern performance road bikes, and for good reason.
The big advantage of 2×12 is how tightly spaced those gears are. Smaller jumps between gears mean you can always find the right gear for your cadence — that comfortable pedaling rhythm — whether you're cruising on flat roads or climbing a steep hill. You also get a wide overall range, so you have both low gears for climbing and high gears for fast descents.
If you're buying a new road bike for fitness riding, racing, or long-distance events, 2×12 is what most manufacturers are building around. Parts and replacement cassettes are widely available, and you're getting the latest drivetrain technology. It's the safe, smart choice for most road riders shopping today.