Okay, it really doesn't look like this story's gonna go away... it's just getting bigger. Trump is imposing more tariffs on goods from China – way more than last time.
What it means: Trump thinks China is disrespecting the rules of trade in the way it deals with America, in particular because he thinks they're taking American 'intellectual property' (which just means knowledge of how to do things) without permission or due process.
The point? Tariffs are basically just extra taxes, which push up the price of Chinese products in the US, making them less appealing to American consumers (who he's hoping will buy American products instead).
But China's said it's going tit-for-tat in this, and will impose equal tariffs on American goods every time the US raises them. This is escalating reaaaally quickly.