2×10 (20-speed) is a perfectly functional setup for getting into road cycling. You'll typically find it on entry-level bikes equipped with Shimano Tiagra, and it gives you two chainrings up front with a 10-speed cassette in the back — enough gears to handle varied terrain and find a comfortable pedaling rhythm.
The main tradeoffs compared to newer 11- or 12-speed systems are slightly larger jumps between gears and heavier components. In practice, this means you might occasionally feel like you're between gears on steady climbs, and the bike will carry a bit more weight. But for new riders building fitness and figuring out what they need, these differences are minor.
Where 2×10 makes the most sense is on a budget. You can often find solid entry-level road bikes with this drivetrain at prices that leave room for accessories or upgrades later. If you find a great deal on a 2×11 bike, that's worth the step up — but don't let 2×10 stop you from a bike that otherwise fits you well and rides nicely.