One thing this allows us to do, is to express that we are good at or bad at a certain activity. To say that we're good at something, we simply use a verb in the plain form + のが上手. Similarly, if you' don’t like're not good at something, you can use plain form + のが下手.
We already knew how to say he is good at Japanese. Now we're also able to say he is good at speaking Japanese.
|He is good at Japanese.||彼 は 日本語 が 上手 です。kare wa nihongo ga jouzu desu.|
|He is good at speaking Japanese.||彼 は 日本語 を 話すの が 上手 です。kare wa nihongo o hanasuno ga jouzu desu.|