Ants

I observed ants outside today because I new some things about ants through sources such as the discovery channel yet haven't observed them in a long time. When i was looking at them i noticed that most of the ants were in unison of one another. Now I do not know how they all know what specific job to do or how they communicate with such a large population around them. Is it instinct? Or is there ways in which they learn how todo there job with one another in a somehwat peaceful and efficient way? The though of doing work with a thousand people in order to achieve a goal just baffers me and shows just how complex nature can be.