The United States and Britain announced on Thursday that they had reached a deal that would reduce tariffs on some imports, such as steel, cars and ethanol, and deepen the economic relationship between the two countries.

There was plenty of mutual congratulating between President Trump in the Oval Office and Keir Starmer, the British prime minister, who dialed in on a speakerphone. “This is a really fantastic, historic day,” Mr. Starmer said.

As the dust settled, though, it became clearer that this was just a framework for a deal and there could be weeks, if not more, of additional negotiations before it became final. Here’s what we know.

It’s the first trade deal since Trump ramped up tariffs.

Mr. Trump’s rewriting of the global trade playbook shocked financial markets, and his administration has been under pressure to reach deals to reduce uncertainty. Mr. Trump said that this deal would be the first of many.

The Trump administration said it would open up export opportunities worth $5 billion for American businesses, while also bringing in $6 billion in tariff revenue.

But Mr. Trump said the final details were still being written up, and British officials said negotiators would continue to try to reduce tariffs not included in this deal.