How much do adjuncts actually get paid

Hello. The way adjuncts get paid is a bit confusing to me. Aside from teaching, do you have to hold office hours? Are office hours held on campus or can they be online? Do you get paid for office hours? What about grading papers?

I also found a job teaching graduate classes. The pay was not listed. But based on my Google research, I discovered many articles regarding low adjunct pay. Is this isolated to certain colleges/universities or is low pay a universal thing?