"-(으)러" marks the purpose and 나오다 is "come out", so: emerged in order to do something. It covers stepping out of an office or a building — coming out for lunch, went out for dinner, came out to collect this — and being out on a job: I'm not out here filming some "I love Seoul" content, two hours into being out fishing for tuna. Compare 으러 나가다, the same trip framed as leaving rather than as having come out.