I may be mistaken (being surprised at @AndreasBlass' answer that not all retired faculty are "emeritus/emerita" [if gender matters]), but in the U.S. in the last 20+ years it seems that (at R1 universities, and maybe R2s) that "emerit*" just means "retired".
The cutesy wrangle about whether the "e(x) merit*" means "from merit" or "without merit" will probably never go away...
So far as I know, no emeritus faculty get any pay, although there may be some deals about benefits (health care in the U.S., ...) People may get to keep modest offices, in some cases, or be reduced to sharing with several other retirees, depending on status...
With widely available internet, and with crumbling infrastructure at many universities, the supposed advantage of "having an office" is evaporating. Many people have better internet, better control of AC or heat, easier parking, nicer space, ... _at_home_ rather than at the (once-regal?) office space on campus. I have a much smaller chance of getting mugged while working at home, already. I have a thermostat! A clean refrigerator. If I had a nice, big, old-fashioned slate blackboard I'd probably have my research students come to my house instead of going to campus to meet them (and have blackboards, luckily, but no AC, parking difficulties even with paid-for reservations, and traffic...)
Skirting faculty meetings, committee assignments, and administrative overhead is a great perk of being retired/emerit*.
In my experience, though, retired faculty do not teach, although they may participate in seminars. On one hand, there are serious conflicts-of-interest in having people who're paid $0$ teach classes, no matter their competence. On another, ... sure, why not let people who've stopped occupying a paid faculty slot still contribute? Unclear to me the wise solution here.