Contacts are simply NPC's (Non-Player Character) in the Matrix who are looking for Redpills willing to undertake missions for them. These contacts are hidden in buildings, on the streets, in alleys, parks, and even the clubs. Once located they will appear on your world map with a special icon. Just talk to a contact to find out if he or she has something that might be of interest to you.

Which Contact Should I Talk To First?

There is a mission contact named Mercury located in Uriah Industrial, close to the South West Hardline at X:-50 Y:-14 Z:271. As for which Contact you should talk to first its still up for debate, but because of your level this would be the best place to start.

Some say to Save them till you have reached level 50 for something extra to do.