Technically “layoffs” are different from “firing”.

Layoffs are typically high in number, wider reaching, reductions in force just to cut numbers.

Firings are targeted and generally (though they don’t have to be) with cause and have a procedure (performance reviews, improvement plans, warnings, etc.)

Not to say you can’t target a layoff to include all your lower performers, more to say that you can still fire someone outside of a layoff.