[rcstank]

Fired means the role will be backfilled, and the employee was let go for performance reasons or whatever else.

Laid off means the role won’t be backfilled. It could also mean the role was renamed, and they wanted to let the employee go but it looks better for everyone to say it was a layoff.

Let go (at least to me) could mean either.

[wccrawford]

I think Fired means it could be backfilled, but I've seen plenty of instances where the company decided to restructure or do things differently instead of hiring someone else.

Just because they were fired for cause doesn't mean the company wants to keep that job around afterwards.

That said, it is unusual not to say 'laid off' these days unless the person was fired for cause, but the recently media frenzy around the term might have them saying other things instead.