The Amateur Radio Emergency Service, or ARES, is an emergency service communications organization composed of amateur radio operators and sponsored by the Amateur Radio Relay League (ARRL) and Radio Amateurs of Canada (RAC). The organization provides training to local Hams including protocols for net operation and passing traffic. ARES groups may be called upon by local governments to supplement communications during civil emergencies.
Repeaters listed by RepeaterBook can be tagged as an ARES-affiliated repeater.
The primary difference between ARES and RACES is that ARES is organized by amateur radio operators who make their services available to local governments and RACES is organized by the government itself.
By FCC rule, both ARES and RACES members must be unpaid volunteers while operating on amateur radio frequencies.
It is possible, under the War Powers Act, that the amateur radio service could be suspended, even forcing the cessation of amateur radio use by ARES members, but allowing RACES to continue in service. RACES does require an emergency declaration by the government to operate. According to Wikipedia, many ARES members also register as RACES members.