before AI it was a software(s) to screen out your writing in non English classes. it was literally try to “guess” if you are copying from somewhere or making the essay vague or not or , which i find it wierd, because its very subjective. usually in a stem class, thse prof dont have time to read your paper, or a small article, so they use a software to assume you arnt just copying from a site, or it thinks your paper may or may not show relevant details.