Being one not under a parliamentary system of government, it’s a term unfamiliar to me.
This explains it:
https://www.instituteforgovernment.org.uk/explainers/proroguing-parliament

If I’m understanding it correctly, proroguing is a suspension of both Houses of Parliament, called by the monarch (under “advice” from the prime minister). That session ends and it stops most pending legislative proposals, but parliament isn’t dissolved, so MPs retain their seats.

Not clear to me whether pending legislation can be restarted where they left off when parliament is reconvened, or if it has to begin again from square one. Although I suppose that’s a technicality.

... several years ago - as mentioned, at the request of the PM - before J Trudeau.

Imagine a foreign crown shutting down Congress to stop Dem legislation from moving forward.

Clearly, an undemocratic process.