US swing states key to Trump's presidential election win

Because of the Electoral College system in the US, "swing states" were key to Donald Trump's return to the White House. Which states were they, and what do we know about them?

US swing states key to Trump's presidential election win
Because of the Electoral College system in the US, "swing states" were key to Donald Trump's return to the White House. Which states were they, and what do we know about them?