Social wasps colonies, established annually are small but grow quickly, these are the guys that cause most wasp stings. They seem to be everywhere, under eaves, above doors, in bushes and playground equipment. Their characteristic paper nests are quickly and violently defended if you get too close, they can sting more than once.
True yellow jacket nests are usually hidden. That’s why many folks get stung; you don’t know they’re there. Plus their diet makes them pests. They will feed on insects; but in urban and park areas, they scavenge sweets and protein-rich foods in uncovered garbage and outdoor dining areas: they’re aggressive when feeding.
Hornets are less the aggressive wasp: they make paper-enclosed, football-shaped nests in trees and shrubs and under eaves. They are not true hornets; only one North America hornet species exists. Leave them alone to hunt insects, you’ll be fine.
Yellowjackets are in the “umbrella wasp” family, building open nests hanging upside down with cells of a papery material, but with no paper envelope. These wasps are beneficials, because young are fed massive numbers of mashed-up caterpillars, wasp baby food. Because of their close proximity to people these wasps give a mild sting when they defend their homes.