Stormont is a big grey building on a hill just outside Belfast, in Northern Ireland. But when people say "Stormont", they almost never mean the building — they mean the government that sits inside it. So "Stormont says no" means the Northern Ireland government says no, and "Stormont has collapsed again" means the government has stopped working. English does this a lot: we use a place to mean the people who work there, the way people say the White House, or 中南海 in Chinese.

The history matters, because it is why the word feels heavy to people there. Northern Ireland got its own parliament in 1921, and it met at Stormont. In 1969 there was very serious violence, and in 1972 London closed that parliament down and ruled Northern Ireland directly from England instead. Then in 1998 a peace agreement created a new body, the Northern Ireland Assembly, and it also meets at Stormont. So the same word covers the old parliament, the new assembly, and the building that held both — which is part of why some people say it warmly and some say it bitterly.

One more thing you will notice if you read the news: Stormont has stopped working several times since 1998, sometimes for years, because the parties there would not sit together. So in British and Irish news you very often see it with words like suspended, restored, collapsed, or back up and running. It is a normal word in news writing, not formal or old-fashioned, but it assumes you already know what it is — nobody explains it. It is always capital S, and never has "the" in front of it.