What did we learn from the first US presidential debate?

US President Donald Trump and Democratic presidential candidate former Joe Biden (Olivier Douliery/Pool vi AP)

After more than a year of circling each other, US President Donald Trump and his Democratic challenger Joe Biden finally met on the debate stage.

The 74-year-old president and 77-year-old former vice president are similar in age, and they share a mutual dislike. But they differ starkly in style and substance. All of that was evident from the outset on the stage in Cleveland, Ohio.