(All) Contacts are acquaintances and people you know who can do stuff for you or pass you some information, for a price and assuming there's no great personal risk involved. If there is high risk involved, the price tag goes up fast and proportional to the risk. If a higher bidder comes along or the Contact feels slighted, insulted, threatened, or abused, your Contact may very well sell you out. Ask a Contact to point you to a drug dealer's home, then there's a messy fight there a few hours later and the cops come knocking on the Contact's door, he'll probably sing like a canary to save his own hide. And if the cops don't come knocking on his door but there's a substantial reward for information leading to the perpetrator...
An important thing to keep in mind is that Contacts are not Allies. Allies have a higher baseline level of trust associated with them that Contacts lack. As a result, Contacts are much cheaper per point.
Each point of Contacts represents a handful of people (roughly 3-6) your character knows by name and residence/hangout/workplace/phone number. Though these handfuls are often linked in some way (workplace, geographically, group affiliation), it's not an absolute requirement. Contacts should be added to your &GMinfo and include a brief description.
Example: 3 points of Contacts could have 2 points for a large gang (10 people) in southeastern St. Claire that you sometimes hang with at the pool hall. They're good for general word-on-the-street and picking up the odd illegal and not-fancy handgun from time to time. The 3rd point could represent the staff (4-6 people) at Bob's Tavern, a local biker hangout on the outskirts of town where your character is a regular.)