Contacts are people your character meets, and for some reason stays in contact with.
They may be friends, Frenemies, convenient business partners, childhood rival, profession rival, carefully selected target for exploitation.
Maybe it was a one night stand and you accidentally swapped com-links. Contacts should be easy to develop, a friendly Johnson, the detective your team crossed path with once to often, another user on your favorite forum/datahaven. Some random friend of your kid brother. The Taxi Drive you end up accidentally using repeatedly. The ganger sitting around on corner you trade insults with on the way home. The stuffer shack attendant who hands you, the soy-burger you order ever day, or the Pizza dilvery guy.
Contacts can be anyone, and favor for a friend (Aka favor for a contact) are very often the best runs, just b/c they can really, really random.